Board	CBSE
Textbook	NCERT Books
Class	Class 10
Subject	Science
Experiment Name	ph of samples
Category	Class 10 Science Lab Manual

NCERT Class 10 Science Lab Manual Cleaning Capacity of Soap in Hard and Soft Water

Introduction
> Water is used for washing along with the soap. The effectiveness and cleansing action of soap depends on the type of water.
> Soft water: The type of water which produces lather with the soap is called soft water. Washing of clothes is very effective and easy in soft water.
> Hard water: The type of water which does not produce lather with the soap is called hard water. It contains dissolved salts in it. The soap forms scum with hard water and not fit for laundry purpose.

Practical Based Questions for Class 10 Chemistry

Types of Hard Water
> Temporary hard water contains dissolved hydrogen carbonate ions, HCO₃^–, of calcium and magnesium.
> Removal of temporary hardness: When water is heated, these ions decompose (break down) to form carbonate ions, CO₃^2-. The carbonate ions in the boiled water react with dissolved calcium and magnesium ions to form calcium carbonate and magnesium carbonate which is insoluble in water and can be removed by filtration. The residue is the insoluble calcium or magnesium carbonate and the filtrate is the soft water.
> Equations:

> Permanent hard water contains dissolved sulphate ions, (SO₄^2-) and chloride ions (Cl^–) of calcium and magnesium. These do not decompose when heated. The ions remain dissolved and do not react with calcium and magnesium ions so the water stays hard even when boiled.
> Soaps do not produce any lather with hard water.
> Removal of permanent hardness of water: The permanent hardness can be removed by boiling it with washing soda, i.e., sodium carbonate (Na₂CO₃ )
> When the hard water is heated with sodium carbonate the double displacement reaction takes place. The insoluble calcium and magnesium carbonates are formed and can be removed by filtration.
> Equations:

> Traditional soaps are ionic compounds which dissolve in water forming a long singly charged hydrocarbon negative ion (anion), which is balanced by a singly charged metal positive ion e.g. Na⁺.
> Soap molecules have a hydrophilic ‘head’ (‘water liking’) and a hydrophobic ‘tail’ (‘water hating’).
> When you shake soap with an oily/greasy material (washing clothes or scrubbing a surface), the oil/grease breaks up into tiny droplets or globules and removed from the surface to which they were attached.
> The long ‘hydrocarbon’ hydrophobic tail of the soap dissolves in the oil or grease globule and the negative head is on the surface of the globules/droplets but in contact with water.
> The long ‘hydrocarbon’ hydrophobic tail can only interact at the molecular level with oil/grease. It is attracted to oil and grease.
> The ‘ionic’ hydrophilic head can only interact with water and forms weak bonds with water.
> Two negative hydrophilic heads cannot interact with each other and tend to repel each other, but strongly interact with water.
> The hydrophobic end takes the oil/grease with it and the hydrophilic end gets washed away with the water carrying its tail which is hydrophobic along with the oil/grease.

Science Lab Manual Class 10 Experiment – 7

Aim
To study the comparative cleaning capacity of a sample of soap in soft and hard water.
Theory
> Soap: It is the sodium or potassium salt of long-chained carboxylic acids.

Cleansing Property of Soap
> Soaps when mixed in water its ionic end dissolves in water but the long chain of carboxylic acid does not dissolve in water but dissolves in oil.
> The soap molecules form structures called ‘micelles’.
> The ionic end is towards the water and the non-ionic end faces towards the oil.
> This forms emulsion in water.

> The soap micelles thus helps.in dissolving the dirt in water and we can wash clothes clean.
> Soft water: The water with no salt in it.
> Hard water: The water with dissolved salt in it. It may be calcium or magnesium salts.
> For cleansing purpose, the foam needs to be produced which depends on free availability of hydrophobic portion of soaps (or alkyl group).
> In soft water, soap shows the cleansing property by forming foam.
> In hard water, hydrophobic end of soap is trapped due to scum or precipitation with the calcium and magnesium salts. This makes the hard water unsuitable for washing.

Materials Required
Two test tubes, test tube stand and measuring cylinder.
Chemical required: Samples of hard and soft water, soap solution and cooking oil.

Procedure (Part A)

1. Take 10 mL of distilled water (soft water) in a test tube. Label it as ‘A’.
2. Take 10 mL of hard water (water from hand-pump, underground water) in another test tube. Label it as ‘B’.
3. In both the test tubes, add few drops of soap solution.
4. Shake the test tubes ‘A’ and ‘B’ vigorously for an equal period of time. Keep them in the test tube stand and record your observations.

Observations
1. In test tube A, soap formed lather or foam.
2. In test tube B, white precipitate was formed with no lather or foam.

Conclusion
Soaps are effective cleaner only in soft water because the soap molecules form lather in soft water. But in case of hard water, the soap molecules do not remain as soap molecules but the ionic end of soap reacts with the salts present in hard water to form curdy white precipitate called scum.

Precautions
1. Use same sample of soap solution for soft water and hard water.
2. Same quantity of soap solution must be added to both the test tubes containing soft water and hard water.
3. The concentration of all test solutions must be same.
4. Shake every test tube for equal number of times and in a similar manner.
Note: If hard water is not available prepare some hard water by dissolving hydrogen carbonate/sulphates/chloride salt of calcium or magnesium in water.

Procedure (Part B)

1. Take 10 mL of distilled water/soft water and add a drop of cooking oil in it. Label this test tube as ‘A’.
2. Take 10 mL of hard water and add a drop of cooking oil in it. Label this test tube as ‘B’.
3. Now, add a few drops of soap solution in both the test tubes ‘A’ and ‘B’.
4. Shake both the test tubes vigorously for the same period of time.
5. Keep them on the test tube stand and record your observations.

Observations
1. The test tube ‘A’ with soft water showed the oil emulsified due to soap solution.
2. The test tube ‘B’ showed no emulsification due to soap solution.

Conclusion
1. The formation of emulsion of oil in soft water by soap shows the effect of soap in cleaning.
2. Soaps are more effective cleaners in soft water than in hard water.

Precautions
1. Use same sample of soap solution for soft water and hard water.
2. Use same cooking oil for soft water and hard water.
3. The concentration of all test solutions must be same.
4. Shake every test tube for equal number of times and in a similar manner.

NCERT Class 10 Science Lab Manual Viva Voce

Question 1:
What is hard water?
Answer:
Water with salts in it is called hard water.

Question 2:
Name two sources of soft water.
Answer:
Rainwater, boiled water.

Question 3:
What is a micelle?
Answer:

When soap molecules are dissolved in water they form an arrangement as shown which is called micelle formation.
The ionic end is pointing outside towards water and non-ionic end is pointing towards the oil.

Question 4:
Name the cleansing agent that can be used in hard water.
Answer:
Detergents.

Question 5:
Would you be able to check if water is hard by using a detergent?
Answer:
No, we cannot test for water if it is hard on using a detergent.

NCERT Class 10 Science Lab Manual Practical Based Questions

Question 1:
Name any two salts present in water.
Answer:
Magnesium sulphate and sodium chloride.

Question 2:
Name two sources of hard water.
Answer:
Groundwater, sea.

Question 3:
Why don’t soaps show cleansing property in hard water?
Answer:
It is because soap’s ionic part combines with salts present in hard water to form insoluble precipitate.

Question 4:
Name two parts of a soap molecule.
Answer:
Soap molecule has two parts, i.e., ionic and non-ionic. The ionic part of soap is hydrophilic and non-ionic part is hydrophobic.

Question 5:
Name few dissolved salts present in hard water.
Answer:
The salts that may be present in hard water are hydrogen carbonates, sulphates, chlorides of calcium or magnesium.

Question 6:
What happens when soap solution is mixed with hard water? Why?
Answer:
Soap forms curdy white precipitate when dissolved in hard water. This is because the ionic end of soap molecule on dissolving in water reacts with the salts of hard water to form the precipitate.

Question 7:
Why are soaps effective in soft water and not in hard water?
Answer:
In hard water it forms insoluble precipitate called scum whereas in soft water it does not form any such compound and hence shows its cleansing property.

Question 8:
How will you test in the laboratory, whether the given sample of water is hard or soft? Name two salts which make the water hard. [Delhi 2011]
Answer:
When few drops of soap solution are added in the given sample of water, if lather is formed with soap then water is soft water. If lather is not formed then water is hard. Calcium chloride and magnesium sulphate salts present in water make the water hard.

Question 9:
Can we test hard water by using detergent? Write one more method other than using soap to test the hardness of hard water. [Delhi 2012]
Answer:
We cannot use detergent for testing hard water. As detergents form lather in both hard water and soft water.
Method to test the hardness of water: If on boiling the water, some insoluble salt’s precipitates (white ppt.) are formed, these precipitates then settl e down and can be removed by filtering the water. The given sample of water is then hard water.

Question 10:
When boilers of water are used for a very long time, then white layers get deposited on inside of these boilers?
How can these white layers be removed? [Outside Delhi 2012]
Answer:
When hard water is used in these boilers, then white scum of salts present in the hard water gets deposited inside the boilers making a white layer. These white layers can be removed by washing the boilers with dil. HCl acid.

Question 11:
Name two salts each of calcium and magnesium which make the water hard. [Outside Delhi 2013]
Answer:
These salts are:
Calcium chloride — CaCl₂ Magnesium chloride — MgCl,
Calcium sulphate — CaSO₄ Magnesium sulphate — MgSO₄.

NCERT Class 10 Science Lab Manual Questions

Question 1:
Do both hard water and soft water produces foam with soap?
Answer:
Only soft water produces foam with soap and hard water does not produce any foam.

Question 2:
Why is scum formed when hard water is treated with soap?
Answer:
Hard water contains calcium and magnesium ions in it which reacts with soap to form insoluble precipitate called scum.

Question 3:
What do you understand by temporary and permanent hardness of water?
Answer:
Temporary hardness of water is due to the presence of calcium and magnesium bicarbonate salt dissolved in water. These salts can be removed by a simple process of boiling the water or on addition of sodium carbonate to hard water.
Permanent hardness of water is due to the presence of chloride and sulphate salts of calcium and magnesium in water. These salts cannot be easily removed and needs ion exchange method for removal.

Question 4:
What is the reaction between soap molecules and ions present in hard water?
Answer:

Questions based on Procedural and Manipulative Skills

1. The correct formula for soap is
(a) C₁₇H₃₅COO⁺-Na^–
(b) C₁₇H₃₅COO^–Na⁺
(c) Both (a) and (b)
(d) None of these

2. A student wanted to make hard water in lab, the correct method of doing so is
(a) Water + Magnesium sulphate and sodium chloride
(b) Water + Magnesium chloride and sodium chloride
(c) Water + Magnesium bicarbonate and sodium bicarbonate
(d) All of the above

3. Hardness of water cannot be detected when we add:
(a) soap
(b) detergent
(c) both (a) and (b)
(d) none of these.

Questions based on Observational Skills

4. The micelle of soap is formed on adding soap to water. What is the correct labelling of this micelle?

(a) (1) hydrophobic end (2) hydrophilic end (3) soap
(b) (1) oil (2) hydrophilic end (3) soap
(c) (1) hydrophilic end (2) hydrophobic end (3) oil
(d) (1) hydrophobic end (2) hydrophilic end (3) oil

5. Soap does not show its cleansing property in
(a) distilled water
(b) mineral water
(c) soft water
(d) salty water

6. Two test tubes P and Q as shown in given figure were used to study the cleansing property of soap. In test tube P foam is formed and in test tube Q scum is formed. The best cleansing property of soap is seen in

7. The correct labelling of test tube A and B when A contains soft water and B contains hard water is:

8. Four test tubes marked as P, Q, R and S, contain solutions of sodium chloride, potassium chloride, calcium chloride and magnesium chloride. On adding soap in it the test tube that gives lather is:
(a) P only (h) Q only
(c) R only (d) both P and Q

9. In the above set-up (Q.8) the scum is formed in:
(a) P (b) R
(c) S (d) R and S

10. Soap solution is added to ethyl alcohol, the correct observation is:
(a) it forms lather.
(b) micelles are formed.
(c) soap dissolves in alcohol.
(d) soap forms scum.

11. A student takes potassium chloride, magnesium sulphate, calcium chloride and calcium sulphate in test tubes A, B, C and D respectively. On adding soap solution to each test tube lather is formed in test tube:
(a) A (b) B
(c) C (d) D

12. If soap is added in hard water which of the .following will not happen?
(a) Scum is formed.
(b) Lather is not formed.
(c) Micelles are formed.
(d) No cleansing action of soap.

13. In hard water, detergent is added. Which of the following observation is true?
(a) Foam is formed.
(b) Cleansing action is seen.
(c) Micelles are formed
(d) All of the above.

14. A student takes about 6 mL of distilled water in four test tubes marked P, Q, R and S. He dissolves sodium sulphate in P, potassium sulphate in Q, calcium sulphate in R and magnesium sulphate in S. After that he adds equal amount of soap solution in each test tube. On shaking these test tubes, he would observe a good amount of lather in the test tubes marked
[All India Delhi 2013]
(a) P and Q (b) Q and R
(c) R and S (d) P and S

Questions based on Reporting and Interpretation Skills

15. The white precipitate that is formed when soap is mixed with hard water is due to
(a) ions in water (b) minerals in water
(c) salts in water (d) acid in water

16. Soap shows its cleansing property due to
(a) micelles formation
(b) lather formation
(c) both (a) and (b)
(d) none of these

17. Soap removes dirt from any surface due to
(a) its tadpole structure
(b) mixture formation
(c) lather formation
(d) hydrophobic and hydrophilic ends

18. Two students A and B were told to test for hard and soft water. They both were given test tubes with soft and hard water respectively and few drops of oil in them. Both the students added soap solution in it and recorded their observations. The correct record is

19. The foaming capacity of soap depends on:
(a) hydrophilic part
(b) saponification
(c) ions present in water
(d) alkyl group.

20. The hardness of water is due to
(a) calcium and magnesium ions
(b) sodium and chloride ions
(c) carbonate and biocarbonate
(d) alkyl group.

21. To remove the temporary hardness of water, we can:
(a) add sodium carbonate to it
(b) add sodium hydroxide to it
(c) filter it
(d) boil it.

22. Hard water required for an experiment is not available in a school laboratory. However, following salts are available in the laboratory. Select the salts which may be dissolved in water to make it hard for the experiment. [Delhi 2013]
1. Calcium Sulphate
2. Sodium Sulphate
3. Calcium Chloride
4. Potassium Sulphate
5. Sodium Hydrogen Carbonate
6. Magnesium Chloride
(a) 1,2 and 4 (c) 3, 5 and 6 (b) 1,3 and 6 (d) 2, 4 and 5

23. In a locality, hard water, required for an experiment, is not available. However, the following salts are available in the school laboratory: [Outside Delhi 2014]
(1) Sodium sulphate
(2) Calcium sulphate
(3) Magnesium chloride
(4) Sodium chloride
(5) Calcium chloride
(6) Potassium sulphate
Which of the above salts may be dissolved in water to obtain hard water for the experiment?
(a) 2, 3 and 5 (b) 1,2 and 5
(c) 1,2, 4 and 6 (d) 3 and 5 only

We hope this CBSE Class 10 Science Lab Manual for Cleaning Capacity of Soap in Hard and Soft Water helps you in your preparation for CBSE Class 10 Board Examination. For any questions pertaining to CBSE Class 10 Science Practicals Cleaning Capacity of Soap in Hard and Soft Water Material, feel free to leave queries in the comments section.

More Resources CBSE Class 10 Lab Manual Practical Skills:

• CBSE Class 10 Science Cleaning Capacity of Soap in Hard and Soft Water Practical Skills
• CBSE Class 10 Maths Lab Manual
• CBSE Class 10 Math Labs with Activity
• CBSE Class 10 Science Practicals Cleaning Capacity of Soap in Hard and Soft Water

Board	CBSE
Textbook	NCERT
Class	Class 10
Subject	Science
Experiment Name	ph of samples
Category	Class 10 Science Lab Manual

NCERT Class 10 Science Lab Manual – Soap Preparation

Introduction
> Traditional soap is a product obtained by the hydrolysis of fats from animals and vegetable oils from plants.
> Soaps are molecules of sodium or potassium salts of long chain carboxylic acids.
> It has tadpole shape with long carboxylic acid chain, non-ionic (hydrocarbon) and ions attached to it like Na+.

> The ionic-end of soap dissolves in water while the carbon chain dissolves in oil.
> Soaps containing sodium salts are formed by heating fat (i.e., glyceryl ester of fatty acid) with aqueous sodium hydroxide solution. This reaction is known as saponification.
> In this reaction, esters of fatty acids are hydrolysed and the soap obtained remain in colloidal form.
> It is precipitated from the solution by adding NaCl.
> The stearic acid molecule C₁₇H₃₅COOH or CH₃(CH₂)₁₆COOH is a typical long chain fatty acid obtained from naturally occurring plant oils and used to make traditional soaps.
> The salt sodium stearate C₁₇H₃₅COO^–Na⁺, formed when stearic acid is neutralised with sodium hydroxide is a typical soap molecule.
> Only sodium and potassium soaps are soluble in water.
> Sometimes fillers are added to the soap to increase their value. For e.g., medicated soaps contain substances of medicinal value. Laundry soaps contain sodium rosinate for better lather formation. Perfumes, glycerol, etc. are also added.
> Generally, potassium soaps are soft to the skin than sodium soaps. These can be prepared by using KOH instead of NaOH.

Advantages of Soap
> Soaps are easily degradable.
> Soaps are soft to the skin.
> It is used in cleaning laundry.

Disadvantages of Soap
> Soap is less effective in cleaning stubborn stains of clothes/laundry.
> Soap forms scum with hard water. Hence, larger amount of soap is needed to wash clothes in hard water.

EXPERIMENT – 6

Aim
To study saponification reaction for preparation of soap.
Theory
Chemically soap is the sodium or potassium salt of a long chain carboxylic acid or glycerol. These carboxylic acids contain 15-18 carbon atoms i.e., long chain of hydrocarbon.
> Hydrophobic end: The end of soap molecule that repels water, it is the hydrocarbon chain.
> Hydrophilic end: The end of soap molecule that is ionic and attracts water.
> Glycerides: They are esters of glycerol, an alcohol containing three hydroxyl groups and fatty acids. Glycerides are present

> Examples of long chain fatty acid.

> Saponification: It is the process in which esters are split with the help of an alkali. Esters are reacted with sodium hydroxide salt to form sodium salt of acid and alcohol.
Chemical reaction of soap
Oil or fat + sodium hydroxide —> soap + glycerol

> In the above reaction, esters of fatty acids are hydrolysed and the soap obtained remain in colloidal form.
> Soap is then precipitated from the solution by adding NaCl.

Materials Required
Beakers, a glass rod, red litmus paper strip, knife, tripod stand, bunsen burner, wire gauze and pair of tongs.
Chemical required: Sodium hydroxide solution, plant oil (Use castor oil + oleic acid) and common salt.

Procedure
1. Take a beaker and add 20 mL of castor oil into it. Heat the oil by constant stirring.
2. Take 20 mL of concentrated sodium hydroxide solution in another beaker.
3. Add the sodium hydroxide solution into the beaker containing hot castor oil. Heat the mixture slowly to boil for about 10 minutes.

4. Dip the red litmus paper strip into this reaction mixture. Note and record your observation.
5. Now, add 5 g of sodium chloride into this mixture with constant stirring and then allow it to cool. Addition of common salt decreases the solubility of soap. The soap molecules get separated from the solution and floats on the surface. This is called salting out of soap.
6. On cooling the beaker, a crust is formed on the surface of the liquid. This crust is called soap.
7. Remove the soap cake and cut it into desired shapes and sizes.
8. The castor oil will produce a soap molecule named sodium oleate (C₁₇H₃₃COONa).

Chemical Equation

Observations
1. The heated mixture of oil and caustic soda forms a pale yellow thick liquid.
2. The red litmus turns blue in this soap solution.

Conclusion
The reaction mixture of (oil) carboxylic acid with sodium or potassium hydroxide produces a soap molecule.
ilk Precautions
1. Be careful while handling concentrated sodium hydroxide as it is corrosive in nature.
2. Do not overheat the beaker while heating.
3. Stir the soap solution carefully so that it does not spill out.
4. Add very small amount of common salt for salting out of soap.

Viva Voce

Question 1:
What are esters?
Answer:
Esters are carbon compounds with general formula RCOOR’ where R and R’ are alkyl groups.

Question 2:
Give an example of commonly used esters.
Answer:
Fats and oils are esters.

Question 3:
What is one molecule of soap?
Answer:
A molecule of soap has tadpole like structure,

Question 4:
What is the pH range of crude soap?
Answer:
pH of crude soap is between 8 to 10.

Question 5:
Name one fatty acid.
Answer:
Stearic acid or oleic acid is an example of fatty acid.

Question 6:
What is the formula of stearic acid?
Answer:
The formula of stearic acid is C₁₇H₃₅COOH.

Question 7:
What is the formula of the soap with stearic acid?
Answer:
The formula of the soap with stearic acid is C₁₇H₃₅COONa.

Question 8:
What is the nature of the soap?
Answer:
Soap is basic in nature. It turns red litmus blue.

Practice Based Questions

Question 1:
What is glycerol?
Answer:
It is an alkanol with 3 hydroxyl groups and the formula is CH₂OH-CHOH-CH₂OH.

Question 2:
How are esters made?
Answer:
Esters can be made by the reaction of alcohol with carboxylic acid.
Alcohol + Carboxylic acid —> Ester + Water

Question 3:
What is saponification?
Answer:
It is the reaction in which fats and oils produce glycerol and salts of fatty acids when reacted with a base.
Fat/oil + NaOH —> Glycerol + Sodium salt of fatty acid (soap)

Question 4:
What happens when soap is dissolved in water?
Answer:
The ions making the soap is dissolved.

Question 5:
What does hydrophobic and hydrophilic parts of soap mean to you?
Answer:
A soap molecule has ionic head which attracts water and is called hydrophilic.
The long hydrocarbon chain stays away from water and is called hydrophobic part of soap.

Question 6:
What is soap?
Answer:
Soap is the sodium or potassium salt of fatty acid.

Question 7:
Name one by-product of soap formation.
Answer:
Glycerol is the by-product of soap formation.

Question 8:
Name the part of the soap molecule which attracts water.
Answer:
The part of the soap molecule which attracts towards water is called hydrophilic part.

Question 9:
Give one advantage of soap over detergent.
Answer:
Soap is biodegradable but detergent is not.

Question 10:
Give one advantage of detergent over soap.
Answer:
Detergent shows its cleansing property in hard water but soap does not show cleansing property in hard water.

Question 11:
What happens when soap is added in hard water?
Answer:
Soap reacts with the salts present in hard water and forms scum and loses its cleansing property.

Question 12:
What are detergents?
Answer:
Detergent are sodium salts of long chain benzene sulphonic acid.

NCERT Lab Manual Questions

Question 1:
Why does a red litmus paper changes its colour when dipped in soap solution? Explain your observation.
Answer:
The red litmus paper changes to blue colour when dipped in soap solution. This is because soap is a basic in nature and has pH more than 7.

Question 2:
Why is it advised to add common salt while preparing the soap?
Answer:
Addition of common salt decreases the solubility of soap.

Question 3:
Can we use Na₂CO₃ instead of NaOH? Explain.
Answer:
On using Na₂CO₃ instead of NaOH the yield will be less and hence it is not advisable to use weak base like Na₂CO₃ for soap preparation.

Question 4:
Was heat evolved or absorbed when sodium hydroxide was added to oil?
Answer:
Heat is evolved when sodium hydroxide is added to oil.

Question 5:
What is the chemical reaction involved in the manufacture of soap?
Answer:
The chemical reaction involved in the preparation of soap is:

Question 6:
Can you devise a method to separate glycerine from the reaction mixture?
Answer:
Glycerine can be separated by adding salt. The soap mixture gets separated into different layers. The top layer is soap and bottom layer is glycerine. The top layer is drained out.

Multiple Choice Questions (MCQs)

Questions based on Procedural and Manipulative Skills

1. Soap is formed from
(a) two hydrophobic compounds
(b) two hydrophilic compounds
(c) reaction of fats and oils on heating
(d) reaction of oil/fat with alkali

2. Soaps act by
(a) forming micelles and trapping the fat/grease with the micelles.
(b) hydrolysis of Na in water
(c) a chemical reaction between dirt and soap
(d) a chemical reaction of fat and dirt.

3. Soaps are precipitated by salting it out with saturated
(a) sodium carbonate
(b) sodium chloride
(c) sodium hydroxide .
(d) sodium bicarbonate

4. Saponification is the hydrolysis of an ester under basic conditions to form a salt of carboxylic acid and
(a) alcohol
(b) ethanol
(c) alkane
(d) aldehyde

5. In soap preparation, the alkali bond on hydrolysis breaks the ester bond to release
(a) fatty acid salt and glycerol
(b) linoleic acid salt and glycerol
(c) ethanoic acid salt and alkane
(d) fatty acid, salt and glycol.

6. Ester is formed by the reaction of
(a) alcohol and base
(b) alcohol and acid
(c) acid and base
(d) base and salt

7. The functional group of acid used in making soap is
(a) —COOH
(b) —COOOH
(c) —CH₃OOH
(d) — HCOOH₂

8. The formula for stearic acid present in oil is
(a) C₁₇H₃₅COOH
(b) C₁₅H₃₁ COOH
(c) C₁₇H₃₁ COOH
(d) C₁₅H₃₇ COOH

9. Glycerol is an alcohol that contains
(a) two hydroxyl groups
(b) three hydroxyl groups
(c) four hydroxyl groups
(d) one hydroxyl group

10. The reaction used for preparation of soap is
(a) esterification
(b) glycolysis
(c) saponification
(d) neutralisation

11. The by-product obtained during preparation of soap is
(a) salt
(b) sodium hydroxide
(c) glycol
(d) glycerol

12. Oil and fats commonly used for preparation of soap are called
(a) carboxylic acids
(b) esters
(c) alcohol
(c) glycerol

13. The pH-range of crude soap obtained during saponification of fats/oil and caustic soda is
(a) 7-8
(b) 8-10
(c) 5-7
(d) 10-12

14.
(a) 3 molecules of glyceride
(b) one molecule of glyceride
(c) 1 compound of glyceride
(d) 3 compounds of glyceride

15. In the preparation of soap, a small amount of sodium chloride (common salt) is added to the mixture of fat and sodium hydroxide. The role of common salt is to [Outside Delhi 2013]
(a) favour the precipitation of soap
(b) enhance the cleansing capacity of soap
(c) increase the weight of the soap to earn money
(d) decrease the acidity of the soap

Questions based on Observational Skills

16. During preparation of soap, common salt, i.e., sodium chloride is added to
(a) decrease the solubility of soap
(b) increase the precipitation of soap
(c) both (a) and (b)
(d) none of the above

17. While preparing soap, sodium chloride is added in the mixture so as to:
(a) complete saponification
(b) complete precipitation
(c) increase the bulk
(d) dissolve the soap.

18. A molecule of soap has four parts labelled on it. The correct pair is

(a) I-hydrocarbon chain
(b) Il-hydrophilic
(c) Ill-ionic head
(d) IV-hydrophobic.

19. Soap solution is:
(a) acidic lb) basic
(c) neutral (d) highly acidic.

20. Soaps are better than detergents because:
(a) soaps are biodegradable
(b) soaps show maximum foaming
(c) soaps are basic in nature
(d) soaps have better cleansing action.

21. Detergents are better than soaps because:
(a) detergents are biodegradable
(b) they work better with hard water
(c) they are acidic in nature
(d) they are cheaper than soaps.

Questions based on Reporting and Interpretation Skills

22. In order to study saponification reaction we first prepare 20% solution of sodium hydroxide. If we record the temperature of this solution just after adding sodium hydroxide flakes to water and also test its nature using litmus, it may be concluded that the process of making this solution is: [Delhi 2014]
(a) exothermic and the solution is alkaline.
(b) endothermic and the solution is alkaline.
(c) endothermic and the solution is acidic.
(d) exothermic and the solution is acidic.

23. While studying saponification reaction for the preparation of soap, the teacher suggested to a student to add a small quantity of common salt to the reaction mixture. The function of common salt in this reaction is to: [Delhi 2014]
(a) reduce the alkalinity of the soap.
(b) reduce the acidity of the soap.
(c) enhance the cleansing capacity of soap, or
(d) favour precipitation of soap.

Scoring Key With Explanation

1. (d) Soap is the sodium salt of fatty acid.
2. (a) Cleansing property of soap is due to micelles formation.
3. (b) Sodium chloride reduces the solubility of soap.
4. (a) As glycerol is the by product of soap formation.
5. (a) The reaction of saponification.
6. (b) Alcohol and carboxylic acid react together to form an ester.
7. (a) Carboxylic acid group is—COOH.
8. (a) Stearic acid is a saturated fatty acid with an 18-carbon chain.
9. (b) Three—OH groups are present in glycerol.
10. (c) Saponification is used for making of soap.
11. (d) 3-OH groups product named glycerol is by product of soap formation.
12. (b) Oils and fats contain esters.
13. (b) Soaps are mild basic compounds.
14. (b) Glycerides are esters of glycerol.
15. (a) Salt helps nfs precipitation of soap.
16. (c) Common salt helps in both the properties.
17. (b) NaCl helps in quick and more precipitation of soap.
18. (c) Mouth of tadpole part is ionic and hydrophilic in nature.
19. (b) Soaps are basic in nature.
20. (a) Bacteria acts on soap molecules to decompose them.
21. (b) Soaps cannot show cleansing property in hard water but detergents can.
22. (a) NaOH in water releases heat and the solution is alkaline in nature.
23. (d) NaCl helps in making more precipitates of soap during saponification.

We hope this CBSE Class 10 Science Lab Manual for Soap Preparation helps you in your preparation for CBSE Class 10 Board Examination. For any questions pertaining to CBSE Class 10 Science Practicals Soap Preparation Material, feel free to leave queries in the comments section.

Watch out for the latest updates on NCERT Books, NCERT Solutions, CBSE Sample Papers, RS Aggarwal Solutions and all resources that we share regularly on CBSETuts.com for K12 Students.

More Resources CBSE Class 10 Lab Manual Practical Skills:

• CBSE Class 10 Science Practical Skills
• CBSE Class 1o Maths Lab Manual
• CBSE Class 1o Math Labs with Activity

Board	CBSE
Textbook	NCERT
Class	Class 10
Subject	Science
Experiment Name	ph of samples
Category	Class 10 Science Lab Manual

NCERT Class 10 Science Lab Manual – Properties of Acetic Acid

Introduction
> Acetic acid is a member of carboxylic acid group and it’s IUPAC name is ethanoic acid.

> Acidic property of CH3COOH is due to its ability to produce hydrogen ions (H⁺) in water.

> The members of the homologous series of the carboxylic acids are found in fruits and in vinegar.
> It belongs to a functional group -COOH.
> Acetic acid is a monocarboxylic acid as it contains only one —COOH group.
> The oxidation of ethanol to ethanoic acid turns alcoholic drinks sour when exposed to air.
> Ethanol + Oxygen —> Ethanoic acid + Water
> This reaction occurs if wine, beer or cider is left out open to the air, it eventually becomes vinegar, not fit for drinking but it is very nice in salad dressing.
> Acetic acid is a weak acid and it ionizes only partially.
> Acetic acid is completely miscible in water to form homogeneous solution.
> In the chemical industry, ethanoic acid can be manufactured on a large scale by oxidising the alcohol named ethanol.

Uses of (carboxylic acids). Acetic acid:

> 5-8% solution of acetic acid in water is called vinegar.
> It is used as a food preservative and in food flavourings.
> Acetic acid is used as coagulant in the manufacture of rubber.
> It is used in the manufacture of various dye stuffs and perfumes.
> It is used in the manufacture of rayon fibre.
> It is used as a solvent.

EXPERIMENT – 5

Aim

To study the following properties of acetic acid (ethanoic acid):
(i) odour (smell)
(ii) solubility in water
(iii) effect on litmus
(iv) reaction with sodium bicarbonate

Theory
Acetic Acid
> The chemical name and formula of acetic acid is ethanoic acid, CH₃COOH.
> The functional group — COOH group is responsible for the properties of acetic acid. —COOH is called carboxyl group.
> It is also called glacial acetic acid, because it freezes at 16.6°C.
> Acetic acid is soluble in water.
> It has vinegar like smell.
> It dissociates in water to form CH₃COO and H+ ions. The dissociation is partial and hence it is called weak acid.
> It turns blue litmus red.
> It reacts with sodium bicarbonate to liberate CO₂ gas.

> Acetic acid reacts with alcohol to form ester. This reaction is called esterification. Esters have fruity smell.

Materials Required
Test tubes, water, litmus paper, test tube stand, a dropper, a beaker, a cork fit in a test tube with bent tube fixed in it.
Chemicals Required: Acetic acid (ethanoic acid), Distilled water, Sodium bicarbonate and Freshly prepared lime water.

Procedure
1. Dilute the given acetic acid with distilled water in a beaker.
2. Pour 5 ml of acetic acid in a test tube and perform the following tests:

S.No.	Test	Experiment	Observation	Inference
1.	Odour	Take 5 mL of acetic acid in a test tube and smell it by wafting.	It has a peculiar pungent smell, (vinegar like smell)	Acetic acid has a vinegar like smell.
2.	Solubility in water	Take 2 mL of acetic acid in a test tube, add 10-15 mL of water and shake.	It dissolves in water to form homogeneous solution.	Acetic acid is soluble in water in all proportions.
3.	Effect on Litmus	Use clean dropper and pour 1-2 drops of acetic acid on blue-litmus paper.	Blue litmus paper turns red.	Acetic acid turns blue litmus red.

4.	Sodium bicarbonate	Take a pinch of sodium bicarbonate in a clean test tube and add 1 mL of dilute acetic acid in the test tube.	Reaction begins, brisk effervescence is seen, a colourless gas is evolved.	Acetic acid and sodium bicarbonate react to liberate CO2 gas.
		Fix a cork with bent delivery tube in the mouth of above test tube. Dip the other end of delivery tube to a test tube containing lime water.	The gas turns lime water milky.	CO2 gas evolved above reacts with calcium hydroxide to form calcium carbonate which is insoluble in water. Ca(OH)2 + CO2 —> CaCO3 + H20 (White precipitate)

Reactions

Precautions
1. Acetic acid should be handled with care.
2. The vapours of the chemicals should not be inhaled.
3. Add only small amount of NaHCO₃ to ethanoic acid to control the intensity of CO₂ evolved.
4. Use freshly prepared lime water for CO₂ test.

Viva Voce

Question 1:
Give the IUPAC name of acetic acid.
Answer:
Ethanoic acid.

Question 2:
Name the functional group present in acetic acid.
Answer:
The functional group in acetic acid is carboxylic group.

Question 3:
State the temperature at which acetic acid freezes.
Answer:
16.6°C.

Question 4:
What is the smell of acetic acid?
Answer:
It has pungent or vinegar like smell.

Question 5:
Give the formula of lime water.
Answer:
Ca(OH)_2.

Question 6:
Name the alkyl group present in acetic acid.
Answer:
Methyl (—CH₃).

Practical Based Questions

Question 1:
Give the molecular formula of acetic acid.
Answer:
CH₃COOH.

Question 2:
Give the structural formula of acetic acid.

Question 3:
State one test to show that acetic acid is an acid.
Answer:
It turns blue litmus paper red.

Question 4:
How can you prepare fresh lime water?
Answer:
Lime and water together gives fresh lime water, the reaction is highly exothermic in nature.
CaO(s) + H₂O)(l) —> Ca(OH)₂(aq)

Question 5:
What happens when sodium bicarbonate reacts with acetic acid?
Answer:
Carbon dioxide gas is evolved and sodium acetate and water is obtained.

Question 6:
Give the test for carbon dioxide.
Answer:
When carbon dioxide is passed through freshly prepared lime water, the lime water turns milky.

Question 7:
In the CO₂ test why does lime water turn milky?
Answer:
Due to the formation of insoluble white precipitate of calcium carbonate.

Question 8:
Write two tests you would perform to detect, whether the given colourless liquid is acetic acid or not. [Delhi 2013]
Answer:
Two tests:
(i) If we put a drop of the given colourless liquid on blue litmus paper, if the blue litmus paper changes to red, then the given acid is acetic acid.
(ii) If we smell the given liquid and the liquid gives a smell like that of vinegar, then the given acid is acetic acid.

Question 9:
What happens when acetic acid is added in a solution of Na₂CO₃ in a test tube? Write the equation for detecting the gas evolved. [All India Delhi 2014]
Answer:
CO₂ gas is evolved with brisk bubbles in this reaction.

White ppt. is formed, when C02 gas is passed through the lime water.

Question 10:
A compound ‘X’ in its aqueous solution form, is added to acetic acid taken in a test tube. Then a gas is evolved. This gas turns lime water milky. Name the compound ‘X’, and the gas evolved. Also write the equation for the reaction. [All India Delhi 2011]
Answer:
Compound ‘X’ can be Na₂CO₃ (Sodium carbonate)
The gas evolved is CO₂ gas.

NCERT Lab Manual Questions

Question 1:
Which gas is evolved when ethanoic acid reacts with sodium hydrogen carbonate?
Answer: Carbon dioxide gas is evolved when ethanoic acid reacts with sodium hydrogen carbonate.

Question 2:
How will you test that the liberated gas is carbon dioxide?
Answer:
By conducting lime water test: Allow the released gas to pass through freshly prepared lime water, if it turns lime water milky then the liberated gas is CO₂.
Note: On passing excess of carbon dioxide through the lime water, the milky precipitate disappears.

Question 3:
How will you show that ethanoic acid is acidic in nature?
Answer:
By litmus paper test: Use blue litmus paper and put two drops of ethanoic acid on it. The blue colour changes to red indicating the acidic nature of ethanoic acid.

Question 4:
Where do you find the use of ethanoic acid in day-to-day food products?
Answer:
Ethanoic acid is used as a preservative in keeping the food products preserved for longer use.

Question 5:
What is the common name of ethanoic acid as sold in the market in the form of its dilute solution?
Answer:
Ethanoic acid in its dilute solution form is known as vinegar in the market.

Question 6:
What type of reaction takes place between ethanoic acid and sodium hydroxide solution?
Answer:
Ethanoic acid neutralizes sodium hydroxide (base) to form salt and water.

Multiple Choice Questions (MCQs)

Questions based on Procedural and Manipulative Skills

1. The number of carbon atoms present in ethanoic acid is:
(a) 1 (b) 3 (c) 2 (d) 4

2. The functional group in ethanoic acid is:
(a) -OH
(b) -CO
(c) -COOH
(d) -CHO

3. The odour of ethanoic acid resembles with
(a) Tomato juice
(b) Kerosene
(c) Orange juice
(d) Vinegar

4. Ethanoic acid reacts with sodium bicarbonate to form:
(a) carbon dioxide gas
(b) sodium ethanoate and carbon dioxide gas
(c) carbon dioxide gas and water
(d) sodium ethanoate, carbon dioxide gas and water

5. The freezing temperature of ethanoic acid is:
(a) 10°C (b) 20°C (c) 18°C (d) 16°C

6. -COOH, present in ethanoic acid is called:
(a) alcohol group
(b) carboxylic group
(c) alkyl group
(d) ketone group

7. Acetic acid reacts with sodium bicarbonate and liberates carbon dioxide gas. The carbon dioxide gas is tested with lime water. Lime water is a solution of:
(a) lemon juice in water
(b) calcium chloride in water
(c) calcium bicarbonate in water
(d) calcium hydroxide in water

8. Acetic acid is:
(a) soluble in water
(b) strong acid
(c) insoluble in water
(d) odourless

9. Following signs are usually shown on the bottles
of commercial acetic acid. The symbols indicate respectively that acetic acid is: [Delhi 2011]

(a) Flammable and corrosive
(b) Radioactive and flammable
(c) Oxidizing and corrosive
(d) Flammable and explosive

10. The pair of safety symbols you notice on the bottles of commercial acetic acid available in the laboratory, is shown in-

Questions based on Observational Skills

11. On adding water to acetic acid the solution obtained would appear as in:

12. 10 mL of acetic acid was added to 10 mL of water and the mixture was shaken, it was observed that:
(a) a heterogeneous solution was obtained
(b) acid formed a layer at the top
(c) acid formed a layer at the bottom
(d) a homogeneous solution was obtained.

13. The odour of ethanoic acid is:
(a) suffocating (b) sweet fruit like
(c) vinegar like (d) burning carbon.

14. Vapours of acetic acid smell:
(a) pungent like vinegar (b) sweet like rose
(c) suffocating like sulphur dioxide
(d) odourless like water

15. A student added acetic acid to test tubes, I, II, III
and IV containing the labelled substances and then brought a burning splinter near the mouth of each test tube. [All India Delhi 2011]

Acetic acid Acetic acid The splinter would be extinguished when brought near the mouth of test tube (a) 1 (b) II (c) III (d) IV

16. A student adds 4 mL of acetic acid to a test tube
containing 4 mL of distilled water. He then shakes the test tube and leaves it to settle. After about 10 minutes he observes: [Delhi 2012]
(a) a layer of water over the layer of acetic acid
(b) a layer of acetic acid over the layer of water
(c) a precipitate settling at the bottom of the test tube
(d) a clear colourless solution

17. On adding acetic acid to sodium hydrogen carbonate in a test tube, a student observes: [All India Delhi 2012]
(a) no reaction
(b) a colourless gas with pungent smell
(c) bubbles of a colourless and odourless gas
(d) a strong smell of vinegar

18. Which one of the following are the correct observations about acetic acid? [All India Delhi 2012]
(a) It turns blue litmus red and smells like vinegar.
(b) It turns blue litmus red and smells like burning sulphur.
(c) It turns red litmus blue and smells like vinegar.
(d) It turns red litmus blue and has a fruity smell.

19. A student takes 2 mL acetic acid in a dry test tube and adds a pinch of sodium hydrogen carbonate to it. He makes the following observations: [Delhi 2013, All India Delhi, 2014]
I. A colourless and odourless gas evolves with a brisk effervescence.
II. The gas turns lime water milky when it is passed through it.
III. The gas bums with an explosion when a burning splinter is brought near it.
IV. The gas extinguishes the burning splinter that is brought near it.
The correct observations are:
(a) I, II and III (b) II, III and IV
(c) III, IV and I (d) IV, I and II

20. A student prepared 20% sodium hydroxide solution
in a beaker containing water. The observations noted by him are given below. [Delhi 2013]
I. Sodium hydroxide is in the form of pellets.
II. It dissolves in water readily.
III. The beaker appears cold when touched from outside.
IV. The red litmus paper turns blue when dipped into the solution.
The correct observations are:
(a) I, II and III (b) II, III and IV
(c) III, IV and I (d) I, II and IV

21. Select the correct observation about dilute solution of acetic acid. [Outside Delhi 2013]
(a) It smells like rotten egg and turn blue litmus red.
(b) It smells like vinegar and turns red litmus blue.
(c) It smells like rotten egg and turns red litmus blue.
(d) It smells like vinegar and turns blue litmus red.

22. In an experiment to study the properties of ethanoic acid, a student takes about 3 mL of ethanoic acid in a dry test tube. He adds an equal amount of distilled water to it and shakes the test tube well. After some time he is likely to observe that: [Outside Delhi 2014]
(a) a colloid is formed in the test tube.
(b) the ethanoic acid dissolves readily in water.
(c) the solution becomes light orange.
(d) water floats over the surface of ethanoic acid.

23. The most appropriate method of testing the colour of a given liquid is
(a) I (b) II (c) III (d) IV

Questions based on Reporting and Interpretation Skills

24. Four test tubes A, B, C and D contain sodium hydroxide, sodium sulphate, ethanoic acid and sodium chloride respectively. In each of the test tubes is added a drop of blue litmus. The colour of litmus will change to red colour in case of:
(a) Test tube A (b) Test tube B
(c) Test tube C (d) Test tube D

25. Reaction of vinegar and baking soda produces:
(a) H₂ gas (b) CO₂ gas
(c) O₂ gas (d) NO₂ gas

26. A sodium salt reacts with ethanoic acid. The reaction liberates a colourless gas that turns lime water milky. The sodium salt is of:
(a) sodium nitrate (b) sodium chloride
(c) sodium hydroxide (d) sodium bicarbonate

27. 10 mL each of acetic acid and water are mixed together and shaken in different test tubes as shown

The resulting mixture after standing would appear as shown in the test tube:
(a) I (b) II (c) III (d) IV.

28. A student added acetic acid to the test tubes I, II, III and IV

The lighted candle would be extinguished when placed near the mouth of the test tube:
(a) I and II (b) II and III
(c) II and IV (d) I and IV

29. Ethyl alcohol reacts with acetic acid in the presence of concentrated H₂SO₄ to form.
(a) ethyl acetate (b) diethyl ether
(c) propanoic acid (d) methyl acetate.

30. Acetic acid turns blue litmus red. What will happen if a few drops of dil. HCl are added to it?
(a) the mixture remains red
(b) the mixture turns blue
(c) the mixture turns colourless
(d) none of the above.

31. Acetic acid is added to a test tube containing a solution of a substance (P), which reacts with acid to form colourless and odourless gas. The gas (Q) turns lime water milky. The substance (P) and (Q) are:
(a) sodium hydroxide (P) and carbon dioxide (Q).
(b) sodium bicarbonate (P) and carbon dioxide (Q).
(c) calcium hydroxide (P) and hydrogen (Q).
(d) ethyl acetate (P) and hydrogen (Q).

32. Four test tubes of acetic acid labelled as A, B, C and D were kept.
In A sodium carbonate was added In B sodium bicarbonate was added In C sodium chloride was added In D sodium hydroxide was added.
Burning candle was brought near the mouth of each test tube. The candle would extinguish near the mouth of test tube.
(a) A and D (b) B and C
(c) A and B (J) B and D

33. Acetic acid solution turns: [Delhi 2011]
(a) blue litmus red
(b) red litmus blue
(c) blue litmus colourless
(d) red litmus colourless

34. Why you add about 2 mL of acetic acid to a test tube containing an equal amount of distilled water and leave the test tube to settle after shaking its contents, then after about 5 minutes what will you observe in the test tube: [Delhi 2014]
(a) A white precipitate settling at its bottom;
(b) A clear colourless solution;
(c) A layer of water over the layer of acetic acid, or
(d) A layer of acetic acid over the layer of water.

For students

> Try the following experiments in a group and record your observation.

1. Dilute the acetic acid as follows: put 2 drops of acetic acid in a test tube and add 15 mL of water in it, taste a drop of this dilute acid.
Observation’.
It tastes like _____
[Precautions: Taste under the supervision of a teacher]

2. Take 2 mL of ethyl alcohol in a test tube and add 2 mL of acetic acid to it, also add 2-4 drops of cone. H2S04. Heat the test tube in water bath.
Record your observation:
1. Smell the product formed in the test tube.
2. Test the sample with blue litmus paper.
3. Name the reaction.

3. Take 5 mL of acetic acid, record its temperature. Now, keep the test tube with acetic acid and thermometer inserted in it, in a beaker containing ice. Record your observations:
Temperature Nature of Acetic Acid
e.g. 20° liquid
18°C liquid
16°C solid

4. Use pH paper to find the acidic nature of acetic acid. Colour of pH paper indicates the strength of acid.

Scoring Key With Explanation

1. (c) “Eth” means two carbon atoms.
2. (c) Functional group of carboxylic acid is—COOH.
3. (d) Vinegar odour resembles ethanoic acid.
4. (d) Like all acids ethanoic acid reacts with NaHCO₃ to release CO₂ gas, water and sodium salt.
5. (d) It is also called glacial acetic acid because it freezes at 16.6°C.
6. (b) Functional group of carboxylic acid is—COOH.
7. (d) Lime water is calcium hydroxide in water i.e., CaO + H₂O —> Ca(OH)₂.
8. (a) It dissolves in water in any ratio.
9. (a) The flame sign indicates flammable and the second symbol is of corrosion.
10. (d) Acetic acid is flammable and corrosive.
11. (b) It is completely soluble in water.
12. (d) It dissolves in water to form homogeneous solution.
13. (c) Acetic acid in water is vinegar.
14. (a) Acetic acid solution is vinegar.
15. (c) CO₂ gas will be released due to presence of carbonate ions in the test tube.
16.(d) Due to complete solubility in water it forms a homogeneous solution.
17. (c) CO₂ gas is released and bubbles are formed.
18. (a) Acetic acid shows acidic properties.
19. (d) All are the properties and tests for CO₂ gas
20. (d) All are the properties of NaOH.
21. (d) These are the properties of acetic acid.
22. (b) Ethanoic acid is soluble in water.
23. (b) The gases should not be smelled directly or kept too close to nose.
24. (c) Acids turn blue litmus red.
25. (b) Baking soda ‘has carbonate ions in it which are released when reacted with acid.
26. (d) Bicarbonates have carbonate ion which is released on reaction with acid.
27. (c) Acetic acid is soluble in water and hence gets clear solution.
28. (c) Test tubes II and IV will release CO₂ gas.
29. (a) The sulphuric acid removes H₂O and esterification reaction is seen.
30. (a) HCl is an acid and will turn blue litmus red.
31. (b) Sodium bicarbonate will release CO₂ gas and Q is CO₂.
32. (c) Both A and B test tubes will release CO₂ gas.
33. (a) Acids turn blue litmus red.
34. (b) It is miscible and dissolves completely in water.

We hope this CBSE Class 10 Science Lab Manual Properties of Acetic Acid helps you in your preparation for CBSE Class 10 Board Examination. For any questions pertaining to CBSE Class 10 Science Practicals Properties of Acetic Acid Material, feel free to leave queries in the comments section.

Watch out for the latest updates on NCERT Books, NCERT Solutions, CBSE Sample Papers, RS Aggarwal Solutions and all resources that we share regularly on CBSETuts.com for K12 Students.

More Resources CBSE Class 10 Lab Manual Practical Skills:

• CBSE Class 10 Science Practical Skills
• CBSE Class 1o Maths Lab Manual
• CBSE Class 1o Math Labs with Activity

Board	CBSE
Textbook	NCERT
Class	Class 10
Subject	Science
Experiment Name	ph of samples
Category	Class 10 Science Lab Manual

NCERT Class 10 Science Lab Manual – Reactivity Series

Introduction
Reactivity of elements
> The atoms of the elements in the periodic table react with each other to form new compounds (except noble gases). The atoms react due to its tendency to lose, gain or share electrons.
> Metals: The atoms of metal will always lose electrons to form positive ions called cations. If the atom readily loses electron at room temperature it is said to be reactive metal than the metal whose atom does not readily lose electron at the room temperature.
> Non-Metals: The atoms of non-metals gains or shares electrons to form negative ions called anions, the atoms of non-metals if readily gains electrons it is said to be more reactive.
> Speed of reaction: We can calculate the speed of reaction of metals by allowing them to react with water at room temperature and collect the hydrogen gas obtained. If the temperature of water, the amount of metal and the amount of water is kept constant, the rate of reactivity can be calculated.

Why displacement reaction?
> To arrange the metals in the increasing or decreasing order of their reactivity one of the commonly used experiment is by checking their displacement rate. This is a reliable technique used, because aluminium is actually a reactive metal but due to the protective coating of aluminium oxide on it, the results may show that aluminium’s reactivity rate is slow.
> Hence the displacement reaction is used to arrange the metals in the reactivity series.

Metal Displacement Reactions
> A more reactive metal will displace (take the place of) a less reactive metal in a metal salt solution.

Non-Metal Displacement Reactions
> This is similar to the metal displacement reactions. In case of halogens, more reactive non-metal will displace the less reactive one from its place.

Metal displacement

> For example, in a given chemical reaction:

> Copper (II) sulphate is blue in colour. When iron nail is dipped in this solution, reaction takes place and blue colour disappears and turns greenish and the iron metal gets coated with pink-brown copper metal.
> A more reactive metal will always displace a less reactive metal.
> If a less reactive metal is added to a more reactive metal salt solution then there will be no reaction.
> For example, iron is less reactive than zinc.
Iron + Zinc sulphate —> No reaction.
> In displacement reactions, the metals compete for the non-metal anion. Here, in the above reaction it is S042- ion.
> The order of the metals in the reactivity series can be worked out by using these type of reactions.

Reactivity series
> The arrangement of metals in decreasing order of their reactivity is called reactivity series or activity series of metals.

Mnemonic	Element	Symbol	Reactivity
Put	Potassium	K	As you can see these metals (excluding carbon, as carbon is used for the reduction of metal from metal oxide ore, all metals below carbon are reduced by it) are above hydrogen in the reactivity series so they react with acids and displace hydrogen gas. Metal + Acid —> Metal salt + Hydrogen
Some	Sodium	Na
Light	Lithium	Li
Color	Calcium	Ca
Metal	Magnesium	Mg
Around	Aluminium	Al
Carbon	Carbon	C
Zone	Zinc	Zn
In	Iron	Fe
The	Tin	Sn
Light	Lead	Pb
Here	Hydrogen	H	H+ ions are responsible for acidic properties.
Comes	Copper	Cu	These elements are below hydrogen so they do not react with acids. (Acids contain H+ ions) Exception: Copper reacts with concentrated nitric acid, the nitrate ions oxidize copper.
Metals	Mercury	Hg
Silver	Silver	Ag
Gold	Gold	Au
Platinum	Platinum	Pt

Note: When metals react with nitric acid they do not release hydrogen gas (except magnesium and manganese) because nitric acid acts as a strong oxidizing agent.

EXPERIMENT 4

Aim
(i) To observe the action ofZn, Fe, Cu and Al metals on the following salt solutions:
(a) ZnSO₄(aq.)
(b) FeSO₄(aq.)
(c) CuSO₄ (aq.)
(d) Al₂(SO₄)₃(aq.)
(ii) Arrange Zn, Fe, Cu and Al metals in the decreasing order of reactivity based on the above result.

Theory
> Reactivity series: The arrangement of metals in decreasing order of their reactivity is called reactivity series. The most reactive metal displaces the less reactive metal from its salt solution.

> Metal salts are coloured

> Reaction of Metals with Salt Solution
(i) Salt solution CuSO₄.

As Al, Zn and Fe can displace Cu from its salt solution hence, all three are more reactive than Cu.
(ii) Salt solution FeSO₄.

As Zn and Al can displace Fe from its salt solution hence, Zn and A1 are more reactive than Fe but Cu is less reactive than Fe.
(iii) Salt solution ZnSO₄.

As only Al metal displaces Zn from its salt solution hence, Al is the most reactive metal among Al, Zn, Fe and Cu.
Al > Zn > Fe > Cu.

Materials Required
Four clean test tubes, marker, a piece of sand paper and test tube stand.
Chemicals required: Aluminium sulphate solution, copper sulphate solution, zinc sulphate solution, iron sulphate solution, metal strips of iron, zinc; copper and aluminium.
Procedure
> Reaction with CuSO₄ solution:
1. Take four clean test tubes.
2. With a marker label them as A, B, C and D.
3. Take copper sulphate solution in each test tube.
4. Dip a small, clean piece of aluminium, zinc, iron and copper metals in test tubes A, B, C and D respectively.
5. Record your observations.

Conclusion: Al, Zn and Fe metals are more reactive than Cu. Hence, Cu is the least reactive metal among the given four metals.
> Reaction with FeSO₄ solution:
1. Take four clean test tubes, labelled as A, B, C, and D.
2. Take FeSO₄ (aq) solution in each test tube.
3. Dip small, clean pieces of aluminium, zinc, iron and copper metals in test tube A, B, C and D respectively.
4. Record your observations.

Conclusion: Al and Zn metals are more reactive than Fe and Cu.

> Reaction with ZnSO₄ solution:
1. Take test tubes A, B, C, and D, clean them.
2. Add ZnSO₄ solution in each test tube.
3. Dip small, clean pieces of Al, Zn, Fe and Cu metal in test tube A, B, C and D respectively.
4. Record your observations.

Conclusion: Al metal is more reactive than Zn metal.

> Reaction with Al₂(SO₄)₃ solution:
1. Take test tubes A, B, C, and D and clean them.
2. Add Al₂(SO₄)₃ solution in each test tube.
3. Dip small, clean pieces of Al, Zn, Fe and Cu metal in test tubes A, B, C and D respectively.
4. Record your observations.

Conclusion: Al metal is not displaced by any of the given metals i.e. Al, Zn, Fe and Cu.

Hence, Al metal is the most reactive metal among the given metals.
1. Al is not displaced by any of the four metals from its salt solution, hence, Al is at the top of the reactivity series.
2. Al can displace Zn from its salt solution but no other metal could displace it. Hence, the reactivity order is Al > Zn.
3. Al and Zn metals can displace Fe metal from its salt solution but Cu cannot.
Hence, the arrangement of metals in decreasing reactivity order is
Al > Zn > Fe > Cu.

I. CuSO₄ solution in each test tube.

II. FeSO₄ solution in each test tube.

III. ZnSO₄ solution in each test tube.

IV. Al₂(SO₄)₃ solution in each test tube.

Precautions
1. Clean the metals by rubbing them with a piece of sand paper before dipping them in the salt solutions.
2. Wash the test tubes after every set of observations of interaction of a particular metal with the four salt solution.
3. Use very little amount of saturated solution of copper sulphate, aluminium sulphate, iron sulphate and zinc sulphate.
4. Use very small pieces of metal every time.
5. Do not touch any chemical.

Viva Voce

Question 1:
What is the colour of copper sulphate solution?
Answer:
The colour of copper sulphate solution is blue.

Question 2:
What is the colour of iron sulphate solution?
Answer:
The colour of iron sulphate solution is green.

Question 3:
When we add Fe in FeSO₄ solution, no change is seen. Why?
Answer:
It is because Fe does not react with FeSO₄ solution.

Question 4:
Name one metal which when added to blue CuSO₄ solution changes it to green colour.
Answer:
Iron metal reacts with blue-coloured copper sulphate solution and changes it into green colour.

Question 5:
What is the colour of Al₂(SO₄)₃ solution?
Answer:
Al₂(SO₄)₃ solution is colourless.

Question 6:
Complete the given chemical equation Fe(s) + CuSO₄(aq) —>
Answer:
Fe(s) + CuSO₄(aq) —> FeSO₄(aq) + Cu(s)

Practical Based Questions

Question 1:
What is the activity series of metals?
Answer:
The arrangement of metals in the decreasing order of their reactivity is called activity series of metals.

Question 2:
What is displacement reaction?
Answer:
When a more reactive metal displaces the less reactive metal from its salt solution, it is called displacement reaction.

Question 3:
What happens when a piece of zinc metal is introduced into a freshly prepared solution of ferrous sulphate?
Answer:
The colour of ferrous sulphate solution is green and when zinc is added to it the colour fades and becomes colourless.

Question 4:
What happens when Fe (Iron) metal is added to blue colour copper sulphate solution?
Answer:
Iron metal reacts with copper sulphate solution to displace copper and form iron sulphate that is green in colour.
Fe(s) + CuSO₄(aq) —> FeSO₄(aq) + Cu(s)

Question 5:
What happens when A1 metal is added to copper sulphate solution?
Answer:
Al metal reacts with copper sulphate solution to form aluminium sulphate and copper metal is displaced.

Question 6:
Name the least reactive metal among the following: Fe, Zn, Al.
Answer:
Fe is the least reactive metal among Fe, Zn, and AT

Question 7:
What will happen if Fe metal is added to ZnSO₄ solution?
Answer:
No reaction will take place, as Fe metal is less reactive than Zn.

Question 8:
Arrange the given metals in the reactivity series:
Mg, Zn, Cu, Fe, Al
Answer:
The reactivity series of metals is
Mg > Al > Zn > Fe > Cu

Question 9:
Name some metals that will react with aluminium sulphate solution, i.e., Al₂(SO₄)₃.
Answer:
Metals like calcium, sodium and magnesium will react with aluminium sulphate solution.

Question 10:
When you keep aluminium strip in FeSO₄ solution, what change is seen?
Answer:
Aluminium is more reactive than Fe hence it displaces Fe from FeS04 and green colour of FeSO₄ disappears.

Question 11:
Why is Fe metal more reactive than copper metal?
Answer:
Fe readily loses electrons as compared to copper. Hence, it is more reactive than copper metal.

Question 12:
How can you test that a given sample contains water or not?
Answer:
On heating copper sulphate crystals the blue colour of copper slowly changes to light blue and then colourless. The water droplets are collected on the inner part of the test tube.

Question 14:
It is regarded that each molecule of copper sulphate crystals at room temperature contains five water molecules as water of crystallisation. Do you see any difference in them? (Hint: Look at the dehydration reaction of copper sulphate)
Answer:
In one molecule of copper sulphate, five water molecules are present to form crystal. The blue colour of the crystals is due to these five water molecules. But, in anhydrous copper sulphate the water molecules are not present.

NCERT Lab Manual Questions

Question 1:
Why does the colour of copper sulphate solution change, when an iron nail is dipped in it?
Answer:
The iron nail reacts with copper sulphate displace copper and form iron sulphate . Due to the displacement reaction the blue colour of copper sulphate changes to green colour of iron sulphate.

Question 2:
How would you devise the procedure to show that Mg > Fe > Cu in reactivity series? What is the basic principle involved in this Experiment?
Answer:
I will react each metal (Mg, Fe and Cu) with the salt solutions of Mg, Fe and Cu. The metal that will displace two metal ions from the salt solutions will be the most reactive and the one which will not show any colour change in the solutions is the least reactive.
Principle: The most reactive metal will displace the less reactive metal.

Question 3:
Why does the following reaction takes place?
2I^– (aq) + Cl₂ (aq) —> 2l^– (aq) + I₂ (solvated)
Answer:
This is the displacement reaction seen among halogens. Chlorine is more reactive than iodine and hence it displaces iodide ion.

Question 4:
In the following reaction, A and B are metals. BX is a salt of metal B.
A + BX —> AX + B
Which one of the two metals is more reactive? Give reason.
Answer:
Metal A is more reactive than B, because metal A displaces metal B from its salt solution.

Question 5:
Name any two metals that are more reactive than iron.
Answer:
Zinc and magnesium.

Question 6:
Why did the colour of copper (II) sulphate solution, change, when zinc metal was dipped in it?
Answer:
Zinc is more reactive than copper and displaces copper from its solution. Hence, the blue colour of copper sulphate solution becomes colourless.

Question 7:
What is your observation when copper is added in iron (II) sulphate solution?
Answer:
Copper is less reactive than iron and cannot displace iron from iron sulphate solution and there is no colour change.

Question 8:
Why can we safely preserve iron (II) sulphate in a copper vessel whereas the same can’t be safely preserved in zinc vessel?
Answer:
Copper is less reactive than iron and cannot react with iron sulphate. Whereas zinc is more reactive than iron and hence it can react with iron sulphate.

Multiple Choice Questions (MCQs)

Questions based on Procedural and Manipulative Skills
1. When an iron strip was placed in the copper sulphate
solution, the time required for the colour of the solution to change from blue to green will be less if:
(a) it is cooled
(b) it is shaken
(c) it is kept undisturbed
(d) it is heated.

2. The colour of zinc sulphate solution is
(a) white
(b) green
(c) yellow
(d) colourless.

3. Which of the following reaction will not occur?
(a) Al + ZnSO₄
(b) Zn + ZnSO₄
(c) Cu + ZnSO₄
(d) Mg + ZnSO₄.

4. Which of the following reaction will take place?
(a) Fe + FeSO₄
(b) Cu + FeSO₄
(c) Au + FeSO₄
(d) Mg + ZnSO₄.

5. To show that zinc is more reactive than copper, the correct procedure is to
(a) prepare copper sulphate solution and dip a zinc strip in it.
(b) prepare copper sulphate solution and dip a copper strip in it.
(c) heat zinc and copper strips.
(d) add dilute nitric acid on both the strips.

6. On adding iron strip in copper sulphate solution, the reaction takes long time, to make it happen fast we can:
(a) add more iron strips
(b) add more copper sulphate solution
(c) heat the container of reactants
(d) heat iron and add in copper sulphate.

7. You are given two test tubes A and B, with solutions ZnS04 and A12(S04)3, both are colourless. To identify the solutions,
(a) add Zn in test tube A and B
(b) add A1 in test tube A and B
(c) first add Zn and then A1 in test tubes A and B
(d) all the above are correct.

8. Two metals which can displace iron from its solution are:
(a) copper and zinc
(b) zinc and tin
(c) silver and aluminium
(d) zinc and aluminium.

9. P + QR → PQ + R. In the above reaction,
(a) Q displaces P
(b) R is displaced by P
(c) P displaces Q
(d) R displaces Q.

10. Two beakers A and B contain Iron (II) sulphate solution. In the beaker A is placed a small piece of copper and in the beaker B is placed a small piece of zinc. It is found that a grey deposit forms on the zinc but not on the copper. From these observations it can be concluded.
(a) Zinc is most active metal followed by iron and copper.
(b) Zinc is most active metal followed by copper and then iron.
(c) Iron is most active metal followed by zinc and then copper.
(d) Iron is most active metal followed by copper and then zinc.

Questions based on Observational Skills

11. A student took Cu, Fe, Zn and Al strips separately in four test tubes labelled I, II, III and IV respectively. He added 10 mL of freshly prepared ferrous sulphate solution to each test tube as shown below:

Black residue would be obtained in test tubes:
(a) I and II (b) I and III
(c) II and III (d) III and IV.

12. Aluminium powder was added to a solution of copper sulphate. The colour of the solution changed from:
(a) colourless to blue
(b) blue to colourless
(c) light green to blue
(d) reddish-brown to light green.

13. The colour of the coating obtained on a zinc rod on dipping in aqueous copper sulphate solution will be
(a) blue (b) brown
(c) white (d) green.

14. Which one is not observed when aluminium is added to a solution of copper sulphate?
(a) The solution is blue in the beginning.
(b) The final solution becomes colourless.
(c) The final solution becomes light green.
(d) A brown mass is deposited on the surface of aluminium.

15. Copper turnings were added to colourless salt solution. After 10 minutes it was observed that the colourless solution turned to a coloured solution and a shiny metal deposition appears. The colour of the solution and that of the metal would respectively be
(a) yellow and Zn (b) green and Fe (c) red and Sn (d) blue and Ag.

16. Iron filings were added to an aqueous solution of copper sulphate. After some time, on observation, it was found that the colour of the solution has changed from
(a) blue to pale green (b) blue to dark green (c) blue to colourless (d) blue to reddish-brown.

17. Zinc granules were added to zinc sulphate, copper sulphate, aluminium sulphate and iron sulphate solutions as shown below. You would observe the deposition of metal on zinc in test tubes

(a) I and III (b) II and IV
(c) I and II (d) III and IV.

18. A student added a piece of zinc metal in four different test tubes containing different solutions. In which test tube he observed no change?
(a) Test tube with CuSO₄ solution
(b) Test tube with AgNO₃ solution
(c) Test tube with ZnSO₄ solution
(d) Test tube with FeSO₄ solution.

19. A student performed the following four experiments:

He would find the formation of solid deposition on
metal in experiments
(a) II, III (b) I, III
(c) I, II, III (d) II, III, IV.

20. A piece of granulated zinc was dropped into copper sulphate solution. After some time, the colour of the solution changed from
(a) light green to blue
(b) blue to colourless
(c) light green to colourless
(d) blue to yellow.

21. A strip of copper was placed in a beaker containing zinc sulphate solution. On observing the strip the next day, it was noticed that
(a) the copper strip remained as it was
(b) the copper strip became thinner
(c) the copper strip became thicker
(d) the colour of the strip changed.

22. When a few crystals of copper sulphate are dissolved
in water, the colour of the solution obtained would be:
(a) green (b) red
(c) blue (d) brown.

23. Iron filings were added to a solution of copper sulphate. After 10 minutes, it was observed that blue colour of the solution changes and a layer gets deposited on iron filings. The colour of the solution and that of the coating would respectively be
(a) yellow and green
(b) brown and blue
(c) red and greenish-blue
(d) green and reddish-brown.

24. Iron spoon was placed in a glass container holding zinc sulphate solution. What is the right observation?
(a) Zinc sulphate will become green.
(b) Glass container will get cracks.
(c) Iron spoon will get holes in it.
(d) Iron spoon will not show any change.

25. When an aluminium strip is kept immersed in freshly prepared ferrous sulphate solution taken in a test tube, the change observed is
(a) the green solution slowly turns blue.
(b) the lower end of the test tube becomes slightly warm.
(c) a colourless gas with a smell of burning sulphur is observed.
(d) light green solution changes to blue.

26. Solutions of FeSO₄, ZnSO₄, CuSO₄ and Al₂(SO₄)₃ solutions were separately taken in four test tubes and some iron nails were placed in each of the solutions. After a few minutes, it would be observed that the colour of
(a) all the four solutions changed.
(b) solution of ZnSO₄, CuSO₄ and Al₂(SO₄)₃ changed and that of FeSO₄ did not change.
(c) solution of ZnSO₄ and Al₂(SO₄)₃ only changed.
(d) copper sulphate solution only changed.

27. When you place iron nail in copper sulphate solution, the reddish brown coating formed on the nail is
(a) soft and dull.
(b) hard and flaky.
(c) smooth and shining
(d) rough and granular.

Questions based on Reporting and Interpretation Skills

28. 10 mL of freshly prepared iron sulphate was taken in
each of four test tubes. Strips of copper, iron, zinc and aluminium were introduced, each metal in a different test tube. A black residue was obtained in two of them.
The right pair of metals forming the precipitates is
(a) Copper and zinc
(b) aluminium and copper
(c) iron and aluminium
(d) zinc and aluminium

29. Four students were assigned separately the experiment of interaction of an iron nail with a solution of copper sulphate. Each group recorded the observations as [ given below in the table. Which group of students recorded the observations correctly?

30. A student took four test tubes containing solutions of different colours marked I, II, III, and IV as shown below. The test tubes containing copper sulphate solution and ferrous sulphate solution could be the tubes:

31. Four students A, B, C and D noted the initial colour of the solutions in test tubes I. II, III and IV. After inserting
zinc rod in each solution and leaving it undisturbed for two hours, they noted the colour of each solution again.

They recorded their observations in the form of table given below:

Students	Colour of solution	I	II	III	IV
A	Initial	Colourless	Colourless	Light green	Blue
	Final	Colourless	Colourless	Colourless	Colourless
B	Initial	Colourless	Light yellow	Light green	Blue
	Final	Colourless	Colourless	Light green	Colourless
C	Initial	Colourless	Colourless	Light green	Blue
	Final	Light blue	Colourless	Colourless	Light blue
D	Initial	Light green	Colourless	Light green	Blue
	Final	Colourless	Colourless	Dark green	Colourless

Which student noted the colour change in all the four test tubes correctly?
(a) A (b) B (c) C (d) D.

32. Aluminium sulphate and copper sulphate solutions were taken in two test tubes I and II respectively. A few pieces of iron filings were then added to both the solutions. The four students A, B, C and D recorded their observations in the form of a table as given below.

Students	(I) Al2(SO4)3 Solution	(II) Copper Sulphate Solution
A	Colourless solution changes to light green	Blue colour of the solution is retained.
B	Colourless solution remains unchanged	Blue solution changes to green.
C	Colourless solution changes to light blue	Blue colour changes to light green.
D	Colourless solution remains unchanged	Blue colour of the solution fades away.

The correct set of observations have been recorded by student
(a) A (b) B (c) C (d) D.

Scoring Key With Explanaion

1. (d) Heat increases the rate of reaction.
2. (d) Zinc salt solutions are colourless.
3. (c) Cu is less reactive than Zn.
4. (d) Mg is more reactive than Zn.
5. (a) This will show displacement reaction.
6. (c) Increase in temperature speeds up the reaction.
7. (d) All tests will help in identifying the solutions.
8. (d) Both are more reactive than Fe.
9. (b) R is removed from the compound and exists freely.
10. (a) Copper does not react, but zinc reacts with ferrous sulphate solution.
Thus, zinc is more reactive followed by iron and copper.
11. (d) Zn and Al are more reactive than Fe and can displace it.
12. (b) Copper salt is blue in colour and aluminium salts are colourless.
13. (b) Cu is displaced by Zn which is brown in colour.
14. (c) Aluminium salt is colourless and not green in colour.
15. (d) Copper is more reactive than Ag.
16. (a) Fe displaces copper ions.
17. (b) Zinc is more reactive than Cu and Fe.
18. (c) Equilibrium is seen.
19. (c) As per reactivity series.
20. (b) Zinc salt solutions are not coloured.
21. (a) Copper is less reactive than zinc.
22. (c) Cu salt is blue coloured.
23. (d) Ferrous salts are green.
24. (d) Iron is less reactive than Zn.
25. (b) It shows thermite reaction and heat is evolved.
26. (d) Cu is the least reactive metal and can be displaced by all the metals given.
27. (a) The freshly deposited copper is soft and dull.
28. (d) Zinc and alufninium being more reactive will replace iron from iron sulphate.
29. (d) Fe will displace Cu ions to give green colour solution and Cu metal is brown coated.
30. (d) Copper sulphate is blue and ferrous sulphate is green in colour.
31. (a) In first two test tubes, the metal will not react but in other two it will react.
32. (b) Fe is less reactive than Al but more reactive than Cu. Hence, displacement reaction will occur.

We hope this CBSE Class 10 Science Lab Manual Reactivity Series helps you in your preparation for CBSE Class 10 Board Examination. For any questions pertaining to CBSE Class 10 Science Practicals Reactivity Series Material, feel free to leave queries in the comments section.

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• CBSE Class 1o Math Labs with Activity

Board	CBSE
Textbook	NCERT
Class	Class 10
Subject	Science
Experiment Name	Types of Reactions
Category	Class 10 Science Lab Manual

NCERT Class 10 Science Lab Manual Types of Reactions

Types of Reactions Introduction

> Chemical reaction: The reaction in which two or more substances react to form a new product with new properties is called a chemical reaction.
> Chemical reaction shows following properties:

1. The heat is evolved (either absorbed or released), bubbles may be given out, color may change or the pH may change.
2. The reactants react to give a new product. This involves the breaking of old bonds and formation of new bonds between the atoms.
3. The atoms of the reactant, either lose, gain or share electrons to form new compounds.
4. The total mass of the atoms reacting in the reaction is always conserved. The atoms are neither created nor destroyed, its mass and-number remains the same.

Types of chemical reactions: Combination reaction, decomposition reaction, displacement reaction, double displacement reaction, exothermic and endothermic reactions.
> Combination Reaction: When two or more reactants react together chemically to form a single product, the reaction is called combination reaction. The reactants can be two elements, an element and a compound or two compounds.

> Decomposition Reaction: When a compound breaks down to form simpler products, the reaction is called decomposition reaction. Decomposition can occur due to heat, light and electricity.

> Displacement Reaction: Metals have different reactivity, some are more reactive and some are less reactive. When a more reactive metal displaces a less reactive metal from its salt solution, the chemical reaction is called displacement reaction.

> Double Displacement Reaction: When two salt solutions (containing two different metallic ions) react with each other, the less reactive metallic ion is replaced by the more reactive metallic ion. Due to the interchanging of ions two new salts are formed. Such reaction is called double displacement reaction.
If the salt formed in the above reaction is insoluble in water then such reaction is called precipitation reaction.

> Exothermic reaction: In a chemical reaction, when heat is released then it is called exothermic reaction.

> Endothermic reaction: In a chemical reaction when heat is required for the chemical reaction to take place then it is called endothermic reaction.

Extended learning
> SO₂: Sulphur dioxide is a good reductant. In the presence of water, sulphur dioxide is able to decolourize substances. Specifically, it is a useful for bleaching papers and delicate materials such as clothes. Oxygen in the atmosphere reoxidizes the reduced dyes, restoring the colour.
> SO₃: Sulphur trioxide will cause serious bums on both inhalation and ingestion since it is highly corrosive in nature. SO₃ should be handled with extreme care as it reacts with water violently and produces highly corrosive sulphuric acid.

NCERT Class 10 Science Lab Manual Experiment 3

Aim
To perform and observe the following reactions and classify them into:
(a) Combination reaction (b) Decomposition reaction
(c) Displacement reaction (d) Double displacement reaction.

1. Action of water on quick lime.
2. Action of heat on ferrous sulphate crystals.
3. Iron nails kept in copper sulphate solution.
4. Reaction between sodium sulphate and barium chloride solutions.

Theory
Action of water on quick time
> Quick lime is calcium oxide (CaO). It combines with water to form calcium hydroxide [Ca(OH)₂] also called as slaked lime.

> Two substances are combining to form one product, hence it is a combination reaction.
> Heat is released in the reaction, hence it is called as exothermic reaction.
> Slaked lime solution turns red litmus blue, hence it is basic in nature.
> The freshly prepared slaked lime is also called as lime water.
> It turns milky when carbon dioxide gas is passed through it.

Action of heat on ferrous sulphate crystals
> Ferrous sulphate crystals are light green in colour. The colour is due to the water of crystallization.
> On heating the crystals of ferrous sulphate, it undergoes following changes:

> The colour changes to brown and gases are released due to the formation of new compounds.
> Single compound decomposes to form three new compounds, hence it is called as decomposition reaction.
> SO₂ and SO₃ gas turns moist blue litmus paper into red, hence it is acidic in nature.
> SO₂ shows reducing property: It changes the orange colour of acidified potassium dichromate to green when SO₂ gas is allowed to pass through it.
> Water of crystallisation is released by the crystals.
> SO₂ gas has choking smell, do not inhale the gas, keep the mouth of the test tube away from your face.
Iron nails kept in copper sulphate solution

> Iron nails when kept in blue coloured solution of copper sulphate, shows following changes:
(a) The blue colour solution changes slowly into light green colour.
(b) Fe²⁺ ions replace Cu²⁺ ions and form iron sulphate in the solution, hence, this is called as displacement reaction.
(c) Iron nail gets the deposit of reddish copper ions on it.
(d) Fe atom forms Fe²⁺ ions by loss of electrons and undergoes oxidation and Cu²⁺ ions gain electrons to become Cu atom and undergoes reduction.

Reaction between sodium sulphate and barium chloride solutions

> Sodium sulphate solution and barium chloride solution are colourless.
> Mixing of both the solutions gives white colour precipitate due to the formation of barium sulphate
> The exchange of ions takes place in the reaction and is called as double displacement reaction.
> Barium sulphate is insoluble in water and hence it forms precipitate.

Materials Required
A beaker, four test tubes, test tube holder, tongs, test tube stand, a dropper, a piece of sand paper and bunsen burner. Chemicals required: A small piece of quick lime, ferrous sulphate crystals, iron nails (clean and unrusted), copper sulphate solution, sodium sulphate solution, barium chloride solution and distilled water.

Precautions

1. Do not touch quick lime with hands, use tongs.
2. Mixing of quick lime and water releases large amount of heat, so add water drop by drop and use borosil beaker.
3. For heating, use hard glass tubes.
4. Never inhale any gas, just waft the gas.
5. Do not touch any chemical with hands.
6. Keep the mouth of the test tube away from your face while heating.
7. The iron nails must be cleaned properly by using sand paper before dipping them in copper sulphate solution.

NCERT Class 10 Science Lab Manual Viva Voce

Question 1:
Give two examples of combination reaction.

Question 2:
When lead nitrate is mixed with potassium iodide solution, name the compound that is formed and give yellow precipitate.
Answer:
When lead nitrate and potassium iodide are mixed, it forms lead iodide that is yellow precipitate and the other product is potassium nitrate.

Question 3:
What happens if iron nail is dipped in green-coloured ferrous sulphate solution?
Answer:
There is no change.

Question 4:
What is blue vitriol and green vitriol?
Answer:
Blue vitriol is CuSO₄.5H₂0
Green vitriol is FeSO₄.7H₂0.

Question 5:
What is the chemical name and formula of lime?
Answer:
Calcium oxide, CaO.

Question 6:
Name the type of reaction when blue vitriol, i.e., CuSO₄.5H₂O is heated.
Answer:
It is a decomposition reaction.

Question 7:
What is the chemical formula of limestone?
Answer:
Formula of limestone is CaCO₃

Question 8:
FeSO₄.7H₂O is the formula for ferrous sulphate. What does 7H₂O stand for?
Answer:
7H₂O is water of crystallisation, i.e., one molecule of FeSO₄ needs seven water molecules to form a crystal.

Question 9:
What is the nature of sulphur dioxide and sulphur trioxide gas?
Answer:
Both SO₂ and SO₃ are acidic in nature.

Question 10:
What is the colour of iron and copper metal?
Answer:
The iron metal is grey in colour and copper metal is reddish-brown in colour.

Question 11:
Give the balanced chemical equation to show the reaction between sodium sulphate and barium chloride.
Answer:

NCERT Class 10 Science Lab Manual Practical Based Questions

Question 1:
State three types of decomposition reaction.
Answer:
Three types of decomposition reaction are due to

Question 2:
Barium chloride solution mixes with sodium sulphate solution to form a white precipitate. The precipitate occurs due to which salt.
Answer:
The white precipitate occurs due to formation of barium sulphate.

Question 3:
What happens when zinc is added to blue colour copper sulphate?
Answer:
The blue-coloured copper sulphate becomes colourless.

Question 4:
Iron nail is dipped in blue-coloured copper sulphate solution. What are the observations?
Answer:
Iron nail gets reddish-brown coating and the blue-coloured copper sulphate solution becomes green.

Question 5:
If you add water in lime (CaO), what changes will you observe?
Answer:
The reaction between lime (CaO) and water is highly exothermic. Large amount of heat is released with the formation of Ca(OH)₂ slaked lime.

Question 6:
State the condition necessary for displacement reaction.
Answer:
Displacement reaction is possible only when a more reactive metal displaces the less reactive metal.

Question 7:
Name the colour of the gas formed when lead nitrate is heated.
Answer:
Brown colour gas of nitrogen dioxide is formed.

Question 8:
What is the chemical formula of lime water? What is it commonly called?
Answer:
The chemical formula of lime water is Ca(OH)₂. Ca(OH)₂ is commonly called as slaked lime.

Question 9:
Carbon dioxide gas should be passed through lime water only for a short duration. Explain why?
Answer:
Less carbon dioxide gas will turn lime water milky but excess of CO₂ gas will make it colourless.

Question 10:
What is the chemical obtained when excess CO₂ is passed through lime water?
Answer:
On passing excess of CO₂ gas through lime water, calcium bicarbonate (CaHCO₃ ) is formed which is soluble in water.

Question 11:
What happens when sodium sulphate and barium chloride solution react together?
Answer:
Sodium chloride and a white precipitate of barium sulphate are formed.

Question 12:
What do you mean by an aqueous solution?
Answer:
The solution that is made in water is called as an aqueous solution.

Question 13:
What do you mean by precipitate solution?
Answer:
When the solution obtained is not soluble in water, then we say precipitate is obtained.

Question 14:
Name the products obtained on decomposition of ferrous sulphate crystals.
Answer:
On decomposition of ferrous sulphate crystals, the products obtained are Fe₂O₃, SO₂, SO₃ and 14H₂0, i.e., Iron oxide, sulphur dioxide, sulphur trioxide and water.

NCERT Class 10 Science Lab Manual Questions

Question 1:
Why does the colour of copper sulphate change, when an iron nail is dipped in it?
Answer:
On adding iron nail in copper sulphate the displacement reaction takes place. Iron being more reactive than copper displaces copper to form green solution of iron sulphate and copper (pinkish brown) metal is displaced.

Question 2:
How would you devise the procedure to show that Mg > Fe > Cu in reactivity series?
Answer:
Step 1: Add Mg metal in ferrous sulphate, taken in one test tube and to copper sulphate taken in another test tube, wait for some time and note the observations.
Step 2: Add Fe metal in magnesium sulphate taken in one test tube and to copper sulphate taken in another test tube, wait for some time and record the observations.
Step 3: Add Cu metal in a test tube with magnesium sulphate and to other test tube with ferrous sulphate in it. Observe and record.
You will note that magnesium can displace Fe and Cu from their salt solutions, Fe can displace only copper from its salt solution and Cu cannot displace any of the metals from the salt solutions.
Hence, the reactivity can be checked and proved that Mg is the most reactive metal and copper is the least reactive metal among Mg, Fe and Cu.

Question 3:
What is the basic principle involved in this experiment?
Answer:
The more reactive metal can displace the less reactive metal.

Question 4:
Why the following reaction does take place?

Answer:
Chlorine is more reactive than iodine, hence it displaces the iodide ions from its aqueous solution and release iodine.

Question 5:
Sodium sulphate and barium chloride are ________ (ionic/covalent) compounds.
Answer:
Ionic.

Question 6:
As the white precipitate of barium sulphate is formed ___________ (immediately/sometime after mixing
the two solutions), the reaction between ___________ (ionic/covalent) compounds is ___________ (instantaneous/slow).
Answer:
immediately, ionic, instantaneous.

Question 7:
What may happen on mixing Pb(NO₃)₂ and KCl solutions? Predict (you may try to experimentally verify).
Answer:
The displacement reaction takes place and yellow colour precipitate of lead iodide is formed.

Question 8:
What are the industrial applications of the type of reaction being studied?
Answer:
These reactions are used in the extraction of metals in industries. These reactions are also helpful in packaging, food processing industries.

NCERT Class 10 Science Lab Manual Multiple Choice Questions (MCQs)

Questions based on Procedural and Manipulative Skills

1. The addition of water in lime is
(a) endothermic reaction
(b) decomposition reaction
(c) exothermic reaction
(d) displacement reaction.

2. The compound also known as blue vitriol is

3. The chemical formula for lime is

4. The chemical formula for slaked lime is

5. The chemical formula of lead nitrate is:

6. The reaction of water and quick lime is an example of
(a) combination reaction
(b) exothermic reaction
(c) both (a) and (b)
(d) none of these.

7. How many water molecules are present in a crystal of copper sulphate molecule?
(a) 5
(b) 7
(c) 2
(d) 3.

8. How many water molecules are present in a crystal of ferrous sulphate molecule?
(a) 5
(b) 2
(c) 7
(d) 10.

9. Which of the following is an endothermic reaction?

10. What is the colour of FeSO₄.7H₂O?
(a) blue
(b) green
(c) white
(d) brown.

11. What is the colour of CuSO₄.5H₂O?
(a) blue
(b) green
(c) white
(d) yellow.

12. Four students used different ways of burning magnesium ribbon during an experiment as shown below.
The correct way has been followed by student:

NCERT Class 10 Science Lab Manual Questions based on Observational Skills

13. The copper coin is dipped in blue coloured copper sulphate solution, the colour obtained after half an hour is
(a) reddish
(b) brownish
(c) colourless
(d) blue colour.

14. When iron nail js kept in blue coloured copper sulphate solution, after a while the colour obtained in the test tube for the solution is
(a) blue
(b) brown
(c) green
(d) red.

15. On adding zinc granules to freshly prepared ferrous sulphate solution a student observes that:
(a) a dull brown coating is formed
(b) a black coating is formed
(c) a greyish coating is formed
(d) no coating is formed.

16. A student strongly heats hydrated ferrous sulphate salt in a dry test tube. He would observe a:
(a) yellow residue
(b) brown residue
(c) light green residue
(d) white residue

17. A student while heating solid lead nitrate taken in a test tube would observe:
(a) white residue of PbO₂
(b) green residue of NO₂
(c) yellow residue of PbO
(d) brown residue of NO.

18. A student took solid quick lime in a china dish and added a small amount of water. He heard:
(a) a popping sound
(b) a crackling sound
(c) a hissing sound
(d) no sound at all.

19. The colour of the gas evolved on heating solid lead nitrate is:
(a) yellow
(b) brown
(c) greenish-yellow
(d) green.

20. When a cleaned iron nail is placed in copper sulphate solution, the colour of the solution changes to:
(a) blue
(b) red
(c) pale violet
(d) pale green.

21. When zinc granules are dipped in blue coloured copper sulphate solution, the colour of solution obtained is:
(a) blue
(b) yellow
(c) colourless
(d) brown.

22. In the reaction of sodium sulphate and barium chloride the colour of the precipitate formed is
(a) yellow
(b) green
(c) white
(d) black.

23. An iron nail was dipped in a salt solution. After sometime a reddish brown deposition of the nail was seen. The salt solution could be
(a) Silver nitrate
(b) Sodium sulphate
(c) Aluminium chloride
(d) Copper sulphate

24. The colour of the residue left in the test tube after heating ferrous sulphate which undergoes decomposition is:
(a) yellowish-brown
(b) black
(c) white
(d) grey.

25. When ferrous sulphate is heated strongly name the gas evolved?

26. On heating ferrous sulphate one would get
(a) sweet smell
(b) rotten egg smell
(c) irritating choking smell
(d) none of the above

Science Lab Manual Class 10 Questions based on Reporting and Interpretation Skills

27. On adding water to lime we get:

28. On passing CO₂ gas through slaked lime we get

29. On strong heating of ferrous sulphate crystals the products formed are:

30. Magnesium metal burns in air with dazzling white flame. The type of chemical reaction seen is
(a) combination reaction
(b) decomposition reaction
(c) displacement reaction
(d) double decomposition.

31. The reaction of sodium sulphate and barium chloride produces a precipitate, the product formed that gives ppt. is
(a) sodium chloride
(b) barium sulphate
(c) barium sulphide
(d) none of these.

CBSE Class 10 Science Lab Manual Scoring Key With Explanation

1. (c) Lime is calcium oxide and it releases heat when reacted with water.
2. (b) Copper sulphate crystals are blue in colour.
3. (c) Lime is calcium oxide.
4. (a) Slaked lime is calcium hydroxide.
5. (d) The valency of lead is 2 and nitrate ion is 1.
6. (c) Calcium oxide combines with water to form calcium hydroxide and heat is released.
7. (a) It is water of crystallization which is constant for each salt.
8. (c) It is water of crystallization which is constant for each salt.
9. (a) Heat is used for the reaction to occur.
10. (b) Ferrous salts are green in colour.
11. (a) Copper salts are blue in colour.
12. (c) Magnesium ribbon is to be burnt directly on the burner using tongs.
13. (d) Blue colour remains the same as copper and copper salt solution shows equilibrium.
14. (c) Fe is more reactive than Cu and can displace it.
15. (c) Zinc will displace Fe from its solution. The colour of Fe is greyish-black.
16. (b) FeO is formed which is brown in colour.
17. (c) Lead nitrate decomposes to form lead oxide which is yellow in colour.
18. (b) Highly exothermic reaction has occurred.
19. (b) Nitrogen dioxide gas is released which is brown in colour.
20. (d) Iron will displace Cu to form green colour iron sulphate.
21. (c) Zinc will displace Cu from copper sulphate solution and zinc salt solutions are colourless.
22. (c) Barium sulphate is white precipitate.
23. (d) The salt solution should be copper sulphate (CuSO₄). Iron displaces copper from its salt solution as a result of which a reddish-brown layer of Cu is deposited on iron nail.
24. (a) Iron oxide is formed which is brownish in colour.
25.
26. (c) It is a decomposition reaction in which SO₂ and SO₃ are liberated which are choking.
27. (a) Calcium oxide reacts with water to form calcium hydroxide.
28. (a) Calcium hydroxide reacts with CO₂ to form calcium carbonate.
29. (d) Ferrous sulphate crystals decomposes to form these products.
30. (a) Mg bums in air to combine with oxygen and forms MgO.
31. (b) Double displacement reaction is seen.

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