- 1 Class 10 Science Chapter 1 Important Questions with Answers Chemical Reactions and Equations
- 1.1 Chemical Reactions and Equations Class 10 Important Questions Very Short Answer Type
- 1.2 Chemical Reactions and Equations Class 10 Important Questions Short Answer Type I
- 1.3 Chemical Reactions and Equations Class 10 Important Questions Short Answer Type II
- 1.4 Chemical Reactions and Equations Class 10 Important Questions Long Answer Type
Solved the very best collection of Chemical Reactions and Equations Class 10 Science Important Questions and Answers Chapter 1 Pdf from the latest NCERT edition books, It will help you in scoring more marks in CBSE Exams.
Class 10 Science Chapter 1 Important Questions with Answers Chemical Reactions and Equations
Class 10 Chemistry Chapter 1 Important Questions with Answers Chemical Reactions and Equations
Chemical Reactions and Equations Class 10 Important Questions Very Short Answer Type
Write the balanced chemical equation with the state symbols of the following reaction: Solutions of Barium chloride and Sodium sulphate in water react to give insoluble Barium sulphate and the solution of Sodium chloride. (2017D)
BaCl2 (aq) + Na2SO4 (aq) → BaSO4 (s) + 2 NaCl (aq)
What happens chemically when quick lime is added to water?
Quick lime reacts vigorously with water to produce slaked lime with the release of large amount of heat.
Name a metal for each case:
(i) it does not react with cold as well as hot water but reacts with any other physical state of water,
(ii) it does not react with any physical state of water.
(i) Aluminium (Al)
(ii) Copper (Cu)
Identify the type of reaction in the following example:
2H2 (g) + O2 (g) → 2H2O (I)
It is a combination reaction because in this reaction two substances combine to form a single substance.
Chemical Reactions and Equations Class 10 Important Questions Short Answer Type I
Write the balanced chemical equation for the following reaction and identify the type of reaction and define it.
‘Iron III oxide reacts with Aluminium and gives molten iron and aluminium oxide’. (2012)
Fe2O3 (s) + 2Al (s) → 2Fe (l) + Al2O3 (l) + Heat
- It is a displacement reaction which is highly exothermic. The amount of heat evolved is so large that the metal is produced in the molten state.
- The displacement reaction of iron (III) oxide with aluminium is known as thermite reaction.
Identify the type of reaction from the following equations: (2012)
(i) CH4 + 2O2 → CO2 + 2H2O
(ii) Pb (NO3)2 + 2KI → PbI2 + 2KNO3
(iii) CaO + H2O → Ca(OH)2
(iv) CuSO4 + Zn → ZnSO4 + Cu
Why is silver bromide stored in dark bottles in the laboratories? Write the chemical equation to justify your answer. (2013)
When silver bromide is exposed to light, it decomposes to form silver metal and bromine
When light falls on pale yellow coloured silver bromide, it changes to greyish white due to the formation of silver metal. To prevent the decomposition of silver bromide, it is stored in dark bottles in the laboratories.
When hydrogen gas is passed over heated copper (II) oxide, copper and steam are formed. Write the balanced chemical equation for this reaction and state (i) the substance oxidized and (ii) the substance reduced in the reaction. (2014)
(i) Substance oxidized = H2 (Hydrogen gas)
(ii) Substance reduced = CuO (Copper oxide)
Chemical Reactions and Equations Class 10 Important Questions Short Answer Type II
(a) Give an example for a combination reaction which is exothermic. (2012)
(b) Identify the oxidising agent, reducing agent in the following reaction.
H2S + Cl2 → 2 HCl + S
(c) Name the phenomenon due to which the taste and smell of oily food changes when kept for a long time in open. Suggest one method to prevent it.
(a) When calcium oxide and water combine to form a single product calcium hydroxide, a large amount of heat is also released. Therefore it is a combination reaction which is exothermic.
(c) The phenomenon is rancidity. When fats and oils are oxidised, they become rancid and their smell and taste changes. This phenomenon is called rancidity.
Prevention from rancidity. Antioxidants are added to food containing fats and oils to prevent them from oxidation.
For example: An inert gas such as nitrogen is added to prevent the packed chips from getting oxidised.
2 g of ferrous sulphate crystals are heated in a boiling tube.
(i) State the colour of ferrous sulphate crystals both before heating and after heating.
(ii) Name the gases produced during heating.
(iii) Write the chemical equation for the reaction. (2012)
(i) The colour of the ferrous sulphate crystals is green before heating and changes to brown after heating.
The colour of the crystals changes due to the formation of ferric oxide.
(ii) During heating sulphur dioxide (SO2) and sulphur trioxide (SO3) are produced.
Describe an activity to show a decomposition reaction in which light is used to decompose a reactant.
Write chemical equation of the reaction and state its one use. (2012)
Take about 2 g silver chloride in a china dish. It is first white in colour. Now place this china dish in sunlight for some time. After some time it is observed that white silver chloride turns grey. This is due to the decomposition of silver chloride into silver and chlorine by light.
Silver bromide also decomposes to silver and bromine by light.
Use: This reaction is used in black and white photography.
(a) What is meant by balanced chemical equation? Why chemical equations are balanced?
(b) Balance the chemical equation given below:
Al2O3 + NaOH → NaAlO2 + H2O (2013)
(a) A balanced chemical equation has an equal number of atoms of different elements in the reactants and products. It means a balanced chemical equation has equal masses of various elements in reactants and products.
According to law of conservation of mass, “Matter can neither be created nor destroyed in a chemical reaction Therefore the chemical equations are balanced to satisfy the law of conservation of mass in chemical reactions.
(b) Al2O3 + 2NaOH → 2NaAlO2 + H2O
Write balanced chemical equations for the following reactions:
(a) dilute sulphuric acid reacts with aluminium powder
(b) dilute hydrochloric acid reacts with sodium carbonate
(c) Carbon dioxide is passed through lime water. (2013)
Solid calcium oxide was taken in a container and water was added slowly to it.
(i) State two observations made in the experiment.
(ii) Write the balanced chemical equation of this reaction.
(i) Solid calcium oxide was taken in a container and water was added to it. Observations:
- The mixture produces a hissing sound.
- The beaker feels to be quite hot.
Mention the rules for writing a chemical equation illustrating with the help of example.
Rules for writing a chemical equation:
- The method of representing a chemical reaction with the help of symbols and formulae of the substances involved in it is known as a chemical equation.
- The substances which combine or react are known as reactants.
- The new substances produced in a reaction are known as products.
- The arrow sign (→) pointing towards the right hand side is put between the reactants and products. This arrow indicates that the substances written on the left hand side are combining to give the substances written on the right hand side in the equation.
Zinc metal reacts with dilute sulphuric acid to form zinc sulphate and hydrogen gas.
Zinc + Sulphuric acid → Zinc sulphate + Hydrogen
Putting the symbols and formulae of all the substances in the above words gives equation,
Select (i) combination reaction (ii) decomposition reaction and (iii) displacement reaction from the following chemical equations: (2014)
(i) ZnCO3 (s) → ZnO (s) + CO2 (g)
(ii) Pb (s) + CuCl2 (aq) → PbCl2 (aq) + Cu (s)
(iii) NaBr (aq) + AgNO3 (aq) → AgBr (s) + NaNO3 (aq)
(iv) H2 (g) + Cl2 (g) → 2HCl (g)
(v) Fe2O3 + 2Al → Al2O36 + 2Fe
(vi) 3H2 (g) + N2 (g) → 2NH3 (g)
(i) Decomposition reaction
(ii) Displacement reaction
(iii) Double displacement reaction
(iv) Combination reaction
(v) Displacement reaction
(vi) Combination reaction
(vii) Decomposition reaction
State the kind of chemical reactions in the following examples: (2014)
(i) Digestion of food in stomach
(ii) Combustion of coal in air
(iii) Heating of limestone
(i) Digestion of food in stomach. During digestion, the complex food is broken into simpler form. Therefore it is a type of decomposition reaction.
(ii) Combustion of coal is air. During combustion the coal burns in air to form CO2, H22 along with the evolution of heat. Thus, it is a type of exothermic decomposition reaction.
(iii) Heating of limestone. When limestone is heated strongly, it breaks into CO2 and lime. Thus it is a type of thermal decomposition reaction.
Write the balanced chemical equation for the following reactions: (2014)
(i) Phosphorus burns in chlorine to form phosphorus pentachloride.
(ii) Burning of natural gas.
(iii) The process of respiration.
Identify the type of chemical reactions in the following processes: (2014)
(i) Barium chloride solution is mixed with copper sulphate and a white precipitate is formed.
(ii) On heating copper powder in a china dish, the surface of copper powder becomes black.
(iii) On heating green ferrous sulphate crystals, reddish brown solid is left as residue and a gas having smell of burning sulphur is evolved.
(iv) Iron nails when left dipped in blue copper sulphate solution become brownish in colour and blue colour of copper sulphate solution fades away.
(v) Quicklime reacts vigorously with water releasing large amount of heat.
(vi) Silver nitrate solution reacts with sodium chloride solution and a white precipitate is formed.
- Double displacement reaction.
- Characterised by the formation of precipitate.
In this reaction, Cu is changing into CuO. This is the addition of oxygen. So this is an oxidation reaction.
(iii) When green coloured ferrous sulphate is heated strongly, it decomposes to form brown coloured ferric oxide. A smell of burning sulphur is also obtained due to the formation of sulphur dioxide. In this reaction, one substance is splitting up into three substances so this is a decomposition reaction.
Iron displaces Cu from copper sulphate solution as iron is more reactive than copper. Therefore this is a displacement reaction.
(v) CaO (s) + H2O (l) → Ca(OH)2
This is a combination reaction as two compounds quick lime and water combine to form a single compound slaked lime.
(vi) When silver nitrate solution is added to NaCl solution, then a white precipitate of silver chloride is formed.
This is a double displacement reaction as two compounds react to form two new compounds.
(a) A substance X, an oxide of a metal, is used extensively in the cement industry. This element is found in our bones also. On treatment with water it forms a solution which turns red litmus blue. Identity X and also write the chemical reaction involved.
(b) Choose a metal from the following metals which reacts only with hot water: Sodium, magnesium, iron.
Mention the products formed during the reaction. (2014)
(a) ‘X’ is Calcium oxide (CaO). Calcium oxide reacts vigorously with water to form Calcium hydroxide (slaked lime)
(b) Magnesium reacts with hot water to form Magnesium hydroxide and hydrogen.
Name the substance oxidised and the substance reduced, and also identify the oxidising agent and reducing agents in the following reaction:
(a) 3MnO2 + 4Al → 3Mn + 2Al2O3
(b) Fe2O3 + 3CO → 2Fe + 3CO2
(c) SO2 + 2H2S → 3S + 2H2O (2015)
Substance oxidised = Al
Substance reduced = MnO2
Oxidising agent = MnO2
Reducing agent = Al
Substance oxidised = CO
Substance reduced = Fe2O3
Oxidising agent = Fe2O3
Reducing agent = CO
Substance oxidised = H2S
Substance reduced = SO2
Oxidising agent = SO2
Reducing agent = H2S
(a) In electrolysis of water, why is the volume of gas collected over one electrode double that of gas collected over the other electrode?
(b) (i) What is observed when a solution of potassium iodide is added to a solution of lead nitrate taken in a test tube?
(ii) What type of reaction is this?
(iii) Write a balanced chemical equation to represent the above reaction. (2015)
(a) In electrolysis of water (H2O), the hydrogen goes to one test tube and oxygen goes to another. The two electrodes collect H and O separately.
Since water (H2O) consists of 2 parts of hydrogen and 1 part of oxygen, so, the volume of hydrogen gas (H2) collected over cathode (negative electrode) is double the volume of oxygen gas (O2) collected over anode (positive electrode).
(b) (i) When potassium iodide solution is added to lead nitrate solution, then a yellow precipitate of lead iodide is produced along with potassium nitrate solution.
(ii) This is a double displacement reaction.
(a) What happens when an aqueous solution of sodium sulphate reacts with an aqueous solution of barium chloride? State the physical conditions of reactants in which reaction between them will not take place. Write the balanced chemical equation for the reaction and also mention the type of reaction.
(b) What changes in the colour of iron nails and copper sulphate solution do you observe after keeping the iron nails in copper sulphate solution for about half an hour? (2015)
(a) When barium chloride solution is added to sodium sulphate solution, then a white precipitate of barium sulphate is formed along with sodium chloride solution:
It is an example of a double displacement reaction. In this displacement reaction, two compounds – barium chloride and sodium sulphate react to form two new compounds barium sulphate and sodium chloride. An exchange of ions takes place in this reaction.
For example, the barium ions (Ba2+) of barium chloride react with sulphate ions (SO42-) of sodium sulphate to form barium sulphate (Ba2+ SO42- or BaSO4). In this reaction, barium sulphate is formed as a white, insoluble solid which separates out suddenly from solution.
Reaction will not take place if the reactants are in a solid state.
(b) When iron nails are dipped in copper sulphate solution, then iron sulphate solution and copper metal are formed:
In this reaction, iron displaces copper from copper sulphate solution. The deep blue colour of copper sulphate solution fades due to the formation of light green solution of iron sulphate. This displacement reaction occurs because iron is more reactive than copper. Also a brown substance will be deposited on the iron nail. This substance is nothing but copper metal.
Chemical Reactions and Equations Class 10 Important Questions Long Answer Type
You are provided with a container made up of aluminium. You are also provided with solutions of dil HCl, dil HNO3, ZnCl2 and H2O. Out of these solutions which solution, can be kept in the aluminium container? Name the type of reaction taking place. (2013)
(i) Dilute HCl cannot be kept in aluminium container because aluminium metal reacts rapidly with dil HCl to form aluminium chloride and hydrogen gas.
(ii) Dil HNO3 cannot be kept in aluminium container because aluminium metal reacts with dil HNO3 to form aluminium nitrate and the hydrogen liberated in this reaction is oxidised to water and nitric acid itself is reduced to any of the oxides of nitrogen. (Displacement reaction)
(iii) ZnCl2 solution also cannot be kept in aluminium container because Al is more reactive than Zn, therefore more reactive Al displaces less reactive Zn from its solution (ZnCl2)
Write balanced chemical equations for the following statements:
(i) NaOH solution is heated with zinc granules.
(ii) Excess of carbon dioxide gas is passed through lime water.
(iii) Dilute sulphuric acid reacts with sodium carbonate.
(iv) Egg shells are dropped in hydrochloric acid.
(v) Copper (II) oxide reacts with dilute hydrochloric acid. (2014)