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CBSE Class 12 Term 1 Chemistry Answer Key 2021

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The Central Board of Secondary Education (CBSE) conducted Chemistry Term 1 exam of Class 12 on 14th December 2021. This exam lasted 90 minutes that took place all throughout the country. The chemistry examination consists of both practical and theoretical components. A Practical exam of 15 marks was conducted before the starting of the CBSE Class 12 Boards (Theory) exams. This theory exam of Class 12 Chemistry is worth 35 marks.

The paper was based entirely on the reduced syllabus prescribed by CBSE and was a moderate question paper with few unexpected questions. There were 55 questions in this question paper, and students had to attempt 45 questions out of the total questions. 

CBSE Class 12 Chemistry Term 1 exam was 35 marks, and the time allotted for this paper was 90 minutes. The Chemistry paper consisted of three sections. All questions were MCQ type questions. Read below for a detailed analysis and structure of the paper:

Section

Type of Questions Asked

Number of Questions Asked

Questions to be Attempted

Section-A

Conceptual and Understanding

25

20

Section-B

Application type and Assertion–Reason  

24

20

Section-C

Entirely on Case–study

06

06

Total Number of Questions

55

45

In terms of exam organisation and paper pattern, there have been a lot of changes this year. The CBSE board started looking at the Term-by-Term schedule for 2021-22 after examining all of the factors. So, let’s look at the Paper analysis of CBSE Class 12 Chemistry Term 1 Set 4 in detail.

2021 CBSE Term 1 Class 12 Chemistry paper was found to be of moderate to easy difficulty. There were some difficult questions in Section-B. Section A was scoring as compared to section B. All the questions were from the syllabus and based on the sample paper provided by the CBSE. 

However, Organic chemistry covered more as compared to physical and inorganic chemistry. The case-based question was found to be a little tricky from the average student point of view.

As the Question paper consisted of four sections that consist of traditional MCQs, Assertion and Reason type, Match the column, Case study types of questions, respectively. These questions are mostly covered from chapters: p-Block Elements, Haloalkanes and Haloarenes and Alcohols, Phenols and Ether, as they have the highest weightage in the question paper. After these chapters, Solid State, Solutions and Biomolecules are covered. Each question carried equal marks. 

Here, the Solved Questions Paper (along with the Answers and the explanation in-depth for each question) of the Chemistry CBSE Class 12th Term 1 Exam is provided as: 

CBSE Class 12th Term 1 Chemistry Board Exam Question Paper and Answers Key 2021-22 (SET 4)

Subject- Chemistry 

Term- I

Time allowed- 90 minutes

Maximum Marks- 35

General Instructions

Read the following instructions very carefully and strictly follow them: 

  1. This question paper contains 55 questions out of which 45 questions are to be attempted. All questions carry equal marks.
  2. The question paper consists of three Sections – Section A, B, and C.
  3. Section – A contains 20 questions. Attempt any 16 questions from Q. No. 01 to 20.
  4. Section – B also contains 20 questions. Attempt any 16 questions from Q. No. 21 to 40.
  5. Section – C contains two Case Studies containing 5 questions in each case. Attempt any 4 questions from Q. No. 41 to 45 and another 4 from Q. No. 46 to 50.
  6. There is only one correct option for every Multiple Choice Question (MCQ). Marks will not be awarded for answering more than one option.
  7. There is no negative marking.

SECTION – A 

Question Numbers 1 to 20 are of 1 mark each. Any 16 Questions from Question 1 to 20 are needed to be attempted.  

Question 1: In a crystal of an ionic compound, the ions Q form the ccp lattice and the ions P occupy all the tetrahedral voids. The formula of the compound is  

(a) PQ2  

(b) P2Q  

(c) PQ  

(d) PQ3

Answer: (b)

Question 2: Increasing the temperature of an aqueous solution will cause

(a) Increase in Molarity  

(b) Increase in Molality  

(c) Decrease in Molarity

(d) Decrease in Molality

Answer: (c)

Question 3: Which of the following conditions is correct for an ideal solution?  

(a) ΔHmix = 0 and ΔVmix = 0 

(b) ΔHmix > 0 and ΔVmix > 0  

(c) ΔHmix < 0 and ΔVmix < 0  

(d) ΔHmix > 0 and ΔVmix < 0  

Answer: (a)

Question 4: 2-Bromo-2-methylpropane is allowed to react with alcoholic KOH solution. The major product formed is

Answer: (d)  

Question 5: Which of the following intermediates is formed in the reaction shown below?

CH3 – CH2 – OH + HI ⇢ CH3 – CH2 – I +H2

(a) CH3CH2+OH2

(b) CH3 – CH2+

(c) Both CH3CH2+OH2 and CH3 – CH2+

(d) CH3CH2 – O+– CH2 â€“ CH3 

Answer: (c)

Question 6: Glucose is oxidized by Br2 water to give

Answer: (b)

Question 7: Which of the following has the largest bond angle?  

(a) NH3

(b) H2O  

(c) PH3

(d) NH4+

Answer: (d)

Question 8: Which of the following elements does not show an oxidation state higher than +2?  

(a) Oxygen

(b) Sulphur  

(c) Selenium

(d) Tellurium

Answer: (a)

Question 9: Which of the following is a molecular solid?  

(a) KCl

(b) SiO2

(c) Cu

(d) Ar  

Answer: (d)

Question 10. For the determination of the molar mass of polymers and proteins, which colligative property is used?

(a) Relative lowering in vapour pressure  

(b) Elevation in boiling point  

(c) Osmotic pressure  

(d) Depression in freezing point

Answer: (c)

Question 11: Which of the following molecules is chiral in nature?

Answer: (b)

Question 12: The reaction: 

is an example of

(a) Reimer-Tiemann reaction

(b) Kolbe’s reaction

(e) Williamson’s synthesis

(d) Wurtz reaction  

Answer: (a)

Question 13: Which of the following is fibrous protein?

(a) Albumin

(b) Keratin

(c) Insulin

(d) Globin  

Answer: (b)

Question 14: The acid strength of HF, HCI, HBr and HI increases in the order

(a) HF <HCI < HBr < HI

(b) HI < HBr < HCI <HF  

(c) HBr < HI < HCI < HF

(d) HF < HBr < HI <HCI

Answer: (a)

Question 15: Which is not correct about concentrated H2SO4?

(a) Dehydrating agent  

(b) Oxidising agent

(c) Ka2 > Ka1

(d) It forms two series of salts.

Answer: (c)

Question 16: Pure water boils at 373.15 K and nitric acid boils at 359.15 K. An azeotropic mixture of H2O and HNO3 boils at 393.55 K. Distilling the azeotropic mixture will cause  

(a) Pure nitric acid to distil over first.

(b) Pure water to distil over first.  

(c) One of them to distil over with a small amount of the other.  

(d) both of them to distil over in the same composition as that of the mixture being distilled.

Answer: (d)

Question 17: A 5% (by mass) solution of glucose (molar mass = 180 g/mol) is isotonic with 1% solution (by mass) of a substance ‘X’. The molar mass of ‘X’ is

(a) 36 g/mol

(b) 18 g/mol 

(c) 72 g/mol

(d) 900 g/mol

Answer: (a)

Question 18: An SN1 reaction of an enantiomerically pure chiral alkyl halide gives a product  

(a) with retention of configuration  

(b) with inversion of configuration

(c) with racemisation

(d) with partial racemisation

Answer: (c)

Question 19: In the following reaction,

The product formed is

Answer: (b)

Question 20: α-D-Glucopyranose and β-D-Glucopyranose are

(a) Isomers that differ in configuration at C-5

(b) Geometrical isomers

(c) Functional isomers

(d) Anomers

Answer: (d)

Question 21: Fluorine does not exhibit variable oxidation states due to

(a) Non-availability of d-orbitals in the valence shell

(b) Low bond dissociation enthalpy

(c) High electronegativity

(d) Small size

Answer: (a)

Question 22: The formation of O2+ [PtF6] is the basis for the formation of Xenon fluoride. 

This is because

(a) O2 and Xe have comparable electronegativities.

(b) O2 and Xe have comparable sizes.

(c) O2 and Xe have comparable ionization enthalpies.

(d) O2 and Xe have comparable electron gain enthalpies.

Answer: (c)

Question 23: Chlorobenzene reacts with Cl2 in the presence of FeCl3 giving ortho and para chloro compounds. The reaction is  

(a) Nucleophilic substitution reaction  

(b) Nucleophilic addition reaction  

(c) Electrophilic addition reaction  

(d) Electrophilic substitution reaction

Answer: (d)

Question 24: Phenol is more acidic than ethanol because  

(a) Ethoxide ion is more stable than Phenoxide ion.  

(b) Phenoxide ion is more stable than Ethoxide ion.  

(c) Phenol undergoes electrophilic substitution reaction.  

(d) Phenol undergoes protonation easily.

Answer: (b)

Question 25: Which of the following statements is not correct about amorphous solids?  

(a) Amorphous solids are anisotropic.  

(b) Amorphous solids have a tendency to flow.  

(c) Amorphous solids have short-range order.  

(d) Amorphous solids have an irregular shape.

Answer: (a)

SECTION B

This section consists of 24 Multiple Choice Questions with the overall choice to attempt any 20 questions. In case more than the desirable number of questions are attempted, ONLY the first 20 will be considered for evaluation.

Question 26: An element with a molar mass of 96 g mol-1 forms a cubic unit cell with an edge length of 4 × 10-8 cm. If the density is 10 g cm-3, the nature of the unit cell is (NA = 6 × 1023 mol-1)  

(a) simple cubic

(b) bcc

(c) fcc

(d) End centred cubic

Answer: (c)

Question 27: When 2.5 g of a non-volatile solute was dissolved in 50 mL of water, it gave a boiling point elevation of 0.52 °C. The molar mass of the solute is Kb for water = 0.52 Km-1)

(a) 100 g mol-1  

(b) 50 g mol-1  

(c) 25 g mol-1

(d) 75 g mol-1 

Answer: (b)

Question 28: Which of the following gas is released on heating ammonium dichromate (NH4)2Cr2O7?  

(a) NO2

(b) N2O  

(c) NO

(d) N2

Answer: (d)

Question 29: On its reaction with water and alkalies, the behaviour of SO2(g) is very similar to that of which gas?  

(a) NO2

(b) CO2  

(c) NH3

(d) N2O

Answer: (b)  

Question 30: Which of the following is most reactive towards nucleophilic substitution reaction?

Answer: (a)

Question 31: In the following reaction

Answer: (c)

Question 32: The structure(s) of the major products expected from the mononitration of 3-methyl phenol will be

Answer: ()

Question 33: 1-Phenylethanol may be prepared by the reaction of C6H5MgBr with

Answer: (a)

Question 34: Two among the three components of DNA are 2-deoxyribose and a nitrogen-containing heterocyclic base. The third component is  

(a) D-ribose

(b) Thymine  

(c) Guanine

(d) Phosphoric acid

Answer: (d)

Question 35: Which one among the following bases is usually not present in RNA?

(a) Uracil

(b) Thymine  

(c) Adenine

(d) Guanine

Answer: (b)

Question 36: Glucose on reaction with (CH3CO)2O forms glucose pentaacetate which confirms the presence of  

(a) – CHO group

(b) – COOH group  

(c) Five – OH groups

(d) A straight-chain

Answer: (c)

Question 37: To increase the solubility of CO2 gas in soft drinks, the bottle is sealed under  

(a) Low pressure

(b) High temperature  

(c) Constant pressure

(d) High pressure

Answer: (d)

Question 38: A solution of a pair of volatile liquids A and B shows negative deviation from Raoult’s law. This is because

(a) pA > pA° xA and pB° xB

(b) The intermolecular forces A – A, B – B < A – B.

(c) Both ΔHmixing and ΔVmixing are positive.

(d) All of the above.

Answer: (b)

Question 39: The structure of XeF6 is

(a) Distorted Octahedral  

(b) Regular Octahedral  

(c) Square Pyramidal

(d) Square Planar

Answer: (a)

Question 40: On the basis of ΔH°bond, which of the following has the strongest bond?  

(a) H – I

(b) H – Cl

(c) H – F

(d) H – Br

Answer: (c)

Question 41: Which of the following oxoacids of Sulphur contains peroxide linkage?

(a) H2SO4

(b) H2S2O7  

(c) H2SO3

(d) H2S2O8

Answer: (d)

Question 42: Which of the following reaction is not correct?

(a) 2F2 + 2H2O  4H+ + 4F- + O2

(b) 2I2 + 2H2O  4H+ +4I- +O2

(c) Cl2 + H2O  HCl + HOCl

(d) Br2 +2H2O  HBr + HOBr

Answer: (b)

Question 43: Which of the following belongs to the class of allylic halides?

Answer: (d)

Question 44: Which reagent will be required for one-step conversion of benzenediazonium to phenol?

(a) Cu2Cl2

(b) NaOH (aq)

(c) H2O

(d) Alcoholic KOH

Answer: (c)

Given below are the questions (45 – 49) labelled as Assertion (A) and Reason (R). Select the most appropriate answer from the options given below.  

(a) Both (A) and (R) are true and (R) is the correct explanation of (A).  

(b) Both (A) and (R) are true, but (R) is not the correct explanation of (A).  

(c) (A) is true, but (R) is false.  

(d) (A) is false, but (R) is true.

Question 45: Assertion (A): Relative lowering in vapour pressure is a colligative property.  

Reason (R): Relative lowering in vapour pressure depends upon the mole fraction of pure solvent.

Answer: (c)

Question 46: Assertion (A): ZnO on heating turns yellow.

Reason (R): Excess Zn2+ ions move to interstitial sites and the electron to neighbouring interstitial sites.

Answer: (a)

Question 47: Assertion (A): F2 is a powerful oxidizing agent.

Reason (R): Fluorine shows anomalous behaviour.

Answer: (b)

Question 48: Assertion (A): Monoclinic Sulphur is stable at room temperature.  

Reason (R): Both Rhombic Sulphur and Monoclinic Sulphur have S8 molecules.

Answer: (b)

Question 49: Assertion (A): Reaction of (CH3)3C – Br with CH3ONa gives the majority of 2-methylpropene.  

Reason (R): CH3ONa acts as a strong base.  

Answer: (a)

SECTION C

This section consists of 6 Multiple choice questions with an overall choice to attempt only 5. In case more than the desirable number of questions are attempted, ONLY the first 5 will be considered for evaluation.

Question 50: Match the following:

  I   II
i. Cl2 (g) A. Inert at room temperature
ii. He (g) B. Reducing Agent
iii. N2 (g) C. Bleaching agent
iv. F2 (g) D. Low solubility in blood
v. Moist SO2 (g)  

Which of the following is the best-matched option?

(a) i-B  ii-A  iii-C  iv-D

(b) i-D  ii-B  iii-A  iv-C

(c) i-C  ii-D  iii-A  iv-B

(d) i-A  ii-D  iii-C  iv-B

Answer: (c)

Question 51: Which of the following analogies is correct:

(a) Chloroform-acetone : Positive deviation :: Ethanol-H2O : Negative deviation.

(b) pA = pA° . xA: Henry’s Law :: p = KH . x : Raoult’s Law

(c) total = pA + pB : Non-ideal solution :: total > pA + pB : Ideal Solution

(d) π = CRT : Osmotic Pressure :: P > π : Reverse Osmosis.

Answer: (d)

Question 52: Complete the following analogy:

O-nitrophenol : A :: O-cresol : B 

(a) A: more acidic than phenol  B: less acidic than phenol 

(b) A: less acidic than phenol    B: more acidic than phenol 

(c) A: more acidic than phenol  B: more acidic than phenol 

(d) A: less acidic than phenol    B: less acidic than phenol

Answer: (a)

Case: Read the passage given below and answer the following questions 53-55. 

No crystal is found to be perfect at room temperature. These defects are basically irregularities in the arrangement of constituent particles. These defects can be stoichiometric or Non-stoichiometric. Stoichiometric defects are of two types: Schottky and Frenkel defects. Schottky is basically a vacancy defect while Frenkel is an interstitial defect. Due to non-stoichiometric defects, the formula of the ionic compound is different from the ideal formula. These defects are also of two types : (i) Metal excess defect and (ii) Metal deficiency defect.

Question 53: What type of defect is shown by AgCl? 

(a) Schottky defect

(b) Frenkel defect 

(c) Metal excess defect

(d) Metal deficiency defect

Answer: (b)

Question 54: Which of the following defects lowers the density of the crystal but does not affect the stoichiometry? 

(a) Schottky defect

(b) Frenkel defect 

(c) Metal excess defect

(d) Metal deficiency defect

Answer: (a)

Question 55: Excess of potassium makes KCl crystals violet due to the formation of 

(a) Cation vacancies

(b) Anion vacancies 

(c) F-centres

(d) Interstitial defect

Answer: (c)



Last Updated : 18 Feb, 2022
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