CBSE Sample Papers for Class 12 Chemistry Paper 2 are part of CBSE Sample Papers for Class 12 Chemistry. Here we have given CBSE Sample Papers for Class 12 Chemistry Paper 2.
CBSE Sample Papers for Class 12 Chemistry Paper 2
Board | CBSE |
Class | XII |
Subject | Chemistry |
Sample Paper Set | Paper 2 |
Category | CBSE Sample Papers |
Students who are going to appear for CBSE Class 12 Examinations are advised to practice the CBSE sample papers given here which is designed as per the latest Syllabus and marking scheme, as prescribed by the CBSE, is given here. Paper 2 of Solved CBSE Sample Paper for Class 12 Chemistry is given below with free PDF download solutions.
Time Allowed : 3 Hours
Max. Marks: 70
General Instructions
- All questions are compulsory.
- Question number 1 to 5 are very short answer questions and carry 1 mark each.
- Question number 6 to 10 are short answer questions and carry 2 marks each.
- Question number 11 to 22 are also short answer questions and carry 3 marks each.
- Question number 23 is a value based question and carry 4 marks.
- Question number 24 to 26 are long answer questions and carry 5 marks each.
- Use log table, if necessary. Use of calculators is not allowed.
Questions
Question 1.
Write the formula of compound which is obtained when carbon reacts with conc.H2SO4.
Question 2.
What type of colloid is formed when a liquid is dispersed in a gas? Give an example.
Question 3.
Write IUPAC name of the following compound:
Question 4.
Select benzylic compound from the following pair:
C6H5CH2-CH2Br
C6H5CH(Br)CH3
Question 5.
What is the effect of adding a catalyst on
- activation energy for reverse reaction if ΔrH = -25 kJ.
- Gibbs energy (ΔG) of a reaction.
Question 6.
Draw the structure of the following:
(i) HClO4
(ii) (HPO3)3
Question 7.
(a) Arrange the following compounds in increasing order of their acidic strength:
o-Cresol, m-nitrophenol, benzoic acid.
(b) Write the mechanism for the given reaction:
OR
Write the product formed in following reactions:
Question 8.
An element exist in bcc unit cell having edge length 400 pm and its density is 8 g/cm3. Find its number of unit cells in 16 g of its sample.
Question 9.
Using IUPAG system of nomenclature write formula as coordination compound and also write its name.
- HBF4
- 3NaF . AlF3
Question 10.
Write the overall cell reaction during discharging of a cell which is more efficient then lead cell for invertor.
Question 11.
Write the principle of the following metallurgical forces:
- Zone refining
- Vapour phase refining
- Electrolytic process
Question 12.
Among the following compounds:
Benzyl chloride, Chlorobenzene and l-Phenyl-2-chloropropane
- Which compound will be most reactive towards SN1 reaction?
- Which compound will be most reactive for elimination reaction?
- Which compound will not give SN reaction at all?
Question 13.
Initial cone, of a reactant is 20 g for a first order reaction. Find time required to reduce it to 2 g if half life period for this reaction is 30 minutes.
Question 14.
Write one difference in each of the following pair:
- micromolecular and macromolecular colloids
- physisorption and chemisorption
- Emulsion and sol.
OR
- Why is it essential to wash the precipitate with water before estimating it quantitatively.
- State Hardy Schulze rule.
- Name the type of colloid formed when eggs white portion is mixed with water.
Question 15.
(a) Why are low spin tetrahedral complexes rarely observed?
(b) Define spectrochemical series.
(c) How many isomers are there for octahedral complex, [CoCl2(en)(NH3)2]+ ?
Question 16.
Calculate E0cell and ΔrG° for the following reaction at 25°C
A2+ + B+ → A3+ + B
Given; KC = 1010, IF = 96500 C mol-1
Question 17.
- What type of depect is present in KCl due to which it appears voilet?
- What type of semiconductor is formed when silicon is doped with As?
- Which one of the following is an example of molecular solid CO2 or SiO2?
Question 18.
(a) Which of the following is a polyamide?
Buna-N, Proteins, PMMA
(b) Can enzyme be called polymer?
(c) Write monomer units of Nylon-2 Nylon-6.
Question 19.
Identify the ‘A’, ‘B’ and ‘C in the following reactions?
Question 20.
- Pickles (particularly of mango) have a long shelf-life and do not get spoiled for months. Why?
- Which class of drugs is used in sleeping pills?
- Why is use of aspartame limited to cold food and drinks?
Question 21.
Give reason for the following:
- PCl5 fumes in moist air.
- Chlorine water on long standing loses its yellow colour.
- XeF2 has a linear shape and not a bent structure.
Question 22.
State reason for the following:
- pKb value for aniline is more than that for methylamine.
- Ammonolysis of alkyl halides does not give the corresponding amine in pure state.
- Ethylamine is soluble in water, whereas aniline is not.
Question 23.
Navnita’s mother fell ill and the doctor diagnosed her with pernicious anemia. She felt lethargic and did not have the energy to do work. Navnita helped her mother in household work till she recovered.
- Name the vitamin, deficiency of which causes pernicious anemia.
- Name the sources which will provides this vitamin.
- Mention the values show by Navita.
Question 24.
Account for the following:
- Transition metals show variable oxidation states.
- Transition metals form alloys.
- Usually transition metals have high metting point.
- Most of the transition metals and their compounds are coloured.
- Transition metals form interstitial compounds.
OR
(a) Write all reactions involved in preparation of K2Cr2O7 from chromite ore.
(b) Compare lanthanoids and actinoids with respect to
- oxidation state
- atomic size
- Abundance in earth’s crust.
Question 25.
(a) Suggest type of intermolecular forces acting in following pairs:
- methanol and ethanol
- NaClO4 and water
(b) What mass of NaCl must be dissolved in 65 g of water to lower the freezing point of water by 7.5°C? The freezing point depression constant (Kf) for water is 1.86 K kg mol-1. Assume van’t Hoff factor for NaCl is 1.87. (Molar mass of NaCl = 58.5 g/mol).
OR
(a) A solution is prepared by dissolving 5 g of non-volatile solute in 95 g of water. It has a vapour pressure of 23.375 mm Hg at 25°C. Calculate the molar mass of the solute. (Vapour pressure of pure water at 25°C is 23.75 mm Hg).
(b) Why is it not possible to obtain pure ethanol by fractional distillation? What is the name of such binary solutions which are inseparable by fractional distillation. How many types of such mixture are there?
Question 26.
(a) Write the product in the following reactions:
(b) Distinguish between following pairs of compounds:
OR
(a) Write the reactions involved in the following named reactions
(i) Etard reaction
(ii) Stephen reduction
(b) Write the steps of the following conversions.
(i) Benzaldehyde to acetophenone
(ii) Acetophenone to benzoic acid
(iii) Ethanoic acid to 2-hydroxyethanoic acid
Answers
Answer 1.
CO2 and SO2
C + 2H2SO4 (Conc.) → CO2 + 2SO2 + 2H2O
Answer 2.
Aerosol e.g. fog, mist, cloud etc.
Answer 3.
4-Chloro-4-methylhex-2-en-l-ol
Answer 4.
Answer 5.
- Activation energy for forward and reverse reaction changes by same extent by the catalyst.
- Gibbs energy will remain same it will not be affected by addition of catalyst.
Answer 6.
Answer 7.
(a) o-Cresol < m-nitrophenol < benzoic acid.
Answer 8.
For BCC
Z = 2
a = 400 pm = 400 × 10-10 cm = 4 × 10-8 cm
d = 8 g/cm3
Mass of sample = 16 g
Volume of a unit cell = a3 = (4 × 10-8)3 = 64 × 10-24 cm3
Answer 9.
- H[BF4]
Hydrogen tetrafluoridoborate (III) - Na3[AlF6]
Sodium hexafluoridoaluminate (III)
Answer 10.
It is Ni-Cd cell which is more efficient than lead cell. Its overall reaction during discharge is:
Cd (s) + 2 Ni(OH)3(s) → CdO(s) + 2Ni(OH)2(s) + H2O(l)
Answer 11.
- Zone refining: The principle involved in this press in impurity is more soluble in melt as compare to crystaline metal.
- Vapour phase refining: The element should form a volatile compound that should be dissociated on further heating.
- Electrolytic process: The more basic metal comes in solution and metal ion gets reduced and deposited on cathode i.e. metal having less positive or more negative reduction potential will come in solution.
Answer 12.
- Benzyl chloride (Carbocation is resonance stabilised)
- 1-phenyl-2-chloro propane
- Chlorobenzene (Due to partial double bond character between Cl and benzene ring).
Answer 13.
t1/2 = 30 minutes for a first order reaction
[A]0 = 20 g, [A]t = 2 g, t = ?
Answer 14.
- Micromolecular colloides have very small particle size so large no. of these particles come together to form colloid but in macromolecular colloid particles are of large enough size to form colloid directly on mixing with dispersion medium.
- There is weak van der Walls forces, exist between dispersed phase and dispersion medium in physisorption whereas strong chemical bond exists in case of chemisorption.
- In emulsion, both dispersed phase and dispersion medium are liquid whereas in case of sol, dispersion medium is liquid and dispersed phase is solid.
OR
- The different ions present in solution may get trapped on precipitate so for quantitative estimation these undesirable must washed away.
- Hardy Schulze rule:
- The ions carrying charge opposite to that of sol particles are effective in causing coagulation
- Coagulating power of an electrolyte is directly proportional to the fourth power of the valency of ions causing coagulation.
Coagulating power ∝ (valency)4.
- Lyophilic or macromolecular colloid will form.
Answer 15.
(a) The energy gap between eg and t2g is less in tetrahedral field. This gap is \(\frac { 4 }{ 9 } \) times as that of octahedral field. Thus, electrons will easily jump to higher orbital instead of pairing, to form high spin complexes mostly.
(b) Spectrochemical series: The arrangement of ligand in order of their increasing field strength i.e. increasing crystal field splitting energy (CFSE) values is called spectrochemical series.
Answer 16.
For the reaction A2+ + B+ → A3+ + B
n = 1
= 0.59 × 10
E0cell = 0.59 V
ΔrG0 = -1 × 96500 × 0.59
ΔrG0 = -56935 J
ΔrG0 = -56.935 KJ/mole
Answer 17.
- Metal excess defect (causes F-centre which is responsible for colour)
- n-type semiconductor
- CO2
Answer 18.
(a) Protein
(b) Yes, enzymes are polymer reason being these are proteins.
Answer 19.
(a) ‘A’ NaNO2 + HCl, 0°C to 5°C
‘B’ → HBF4
‘C → NaNO2, Cu, heat
Answer 20.
- Pickles have vegetable oil as an ingredient which acts as preservative and prevents spoilage due to microbial growth.
- Tranquilizers
- It decomposes at cooking temperature.
Answer 21.
- PCl5 + H2O → POCl3 + HCl
- Due to formation of hydrochloric acid and hypochlorous acid, chlorine water loses its yellow colour on long standing.
Cl2 + H2O → HCl + HOCl - Three lone pairs are directed toward equilateral position to minimise the repulsion and fluorine are on axial position hence XeF2 is linear in shape.
Answer 22.
1. In ‘Aniline’ lone pair of electron resonances with 6π electrons of benzene ring and hence not available for donation on the other hand, electron density on nitrogen increases in methylamine due to +I-effect of CH3 group. Hence, aniline has more pKb value than CH3NH2.
2. In ammonolysis, mixture of products are formed reason being primary amine formed form alkyl halide is more reactive than NH3 and secondary amine is more reactive than primary amine and so on, hence mixture of products will form.
RCl \(\underrightarrow { { NH }_{ 3 } }\) RNH2 \(\underrightarrow { RCl } \) RNH-R \(\underrightarrow { RCl } \) R3N
3. Aryl group is more hydrophobic than alkyl group hence hydrogen bonding with aniline is less likely on the other hand, ethylamine can form hydrogen bond with water efficiently.
Answer 23.
- Vitamin B12
- Meet, Fish, egg and Curd
- Helpful and caring nature
Answer 24.
- Due to comparable energy of (n-1)d and ns orbitals transition metals show variable
oxidation states. - Due to comparable size and strong metal-metal bond with other transition and non transition elements, alloys are formed.
- Due to small size and large number of unpaired electrons for metal bond, transition metals have high melting point.
- Due to presence of impaired electrons and d-d transition most of the transition metals and their compounds are coloured.
- Due to suitable size of void in which smaller atoms like H, B, C, N etc. can tightly fix as well as strong M-M bond is responsible for interstitial compound formation.
OR
(a) Reactions involved in preparation of K2Cr2O7 from chromite ore:
(b) Comparison of lanthanoids and actinoids
- Oxidation state: General oxidation state of lanthanoids is +3 some elements also exhibit +2 and +4 oxidation state but actinoids show +3 to +7 all oxidation states i.e. shows variable oxidation state.
- Atomic size: The atomic size decrease in both series but decrease in actinoids is more as compare to actinoids due to poorer shilding of 5f orbital as compare to 4f orbital.
- Abundance in earth’s crust: Lanthanoids exists in earth’s crust but other than first five elements of actinoids all others are prepared in laboratory by nuclear transmutation.
Answer 25.
(a)
- Hydrogen bonding (dipole-dipole interaction)
- Ion-dipole interaction.
(b) It is given that,
Mass of solvent (wA) = 65 g
ΔTf = + 7.5°C = 7.5K
Kf = 1.86 K kg mol-1
i = 1.87
Molar mass of NaCl (mB) = 58.5 g/mol
wB (mass of NaCl) = ?
(b) Ethanol contains water during its manufacturing but due to formation of azeotropic solution at a concentration 95% ethanol and 5% water they have same proportion in solution as well as in vapour state hence can not be separated by fractional distillation. Azeotropic solution are of following two types
- Minimum Boiling Azeotropic solution
- Maximum Boiling Azeotropic solution.
Answer 26.
(ii)
Reagent |
o-Cresol |
Benzoic acid |
NaHCO3 (aq) |
No change |
Bubbles of CO2 evolves briskly |
OR
(a) (i) Etard Reaction: Chromyl chloride oxidised methyl group to a chromium complex which on hydrolysis gives corresponding benzaldehyde.
(ii) Stephen Reduction: Nitriles are reduced to imines with SnCl2 and HC1, which on hydrolysis gives aldehyde
SnCl2 + 2HCl → SnCl4 + 2[H]
We hope the CBSE Sample Papers for Class 12 Chemistry Paper 2 help you. If you have any query regarding CBSE Sample Papers for Class 12 Chemistry Paper 2, drop a comment below and we will get back to you at the earliest.