Class 12 Chemistry Answer Key 2024 Out, For Set 1, 2, 3

Chemistry Answer key 2024

The Central Board of Secondary Education has successfully conducted the CBSE Class 12 Chemistry Exam 2024 on 27 February 2024. The chemistry paper was concluded at 01:30 pm, As the completion of the examination we updated the CBSE Class 12 Chemistry Answer Key 2024 on this page. The students appearing in the examination can match their answers with the unofficial Class 12 Chemistry Answer Key 2024 prepared by the expert facilities of Adda247. 

Class 12 Chemistry Answer Key 2024

Here we have given the complete CBSE Class 12 Chemistry Answer Key 2024 along with Exam Analysis. In CBSE Class 12 Chemistry Answer Key & Exam Analysis, we will cover the difficulty level of the exam, out-of-syllabus questions, and mistakes in the question paper. CBSE Class 12 Chemistry Answer key 2024 is provided for all sections. Section A consists of 16 multiple-choice questions worth one mark each. Section B consists of five short answer questions worth two marks each. After completion of the CBSE Exam for the Chemistry subject, the students must match their responses with the Chemistry Answer Key provided on this page and must check the CBSE Class 12 Chemistry Exam Analysis.

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Answer Key Chemistry Class 12: Overview

CBSE Class 12 Chemistry Answer Key 2024 given on this page is error-free and all the answers are framed by the faculties who have years of experience in teaching Class 12 Chemistry. Below we have given the highlights of CBSE Answer Key Chemistry Class 12. The students must check the brief information of CBSE Class 12 Chemistry Answer Key 2024 provided in the table below.

Class 12 Chemistry Answer Key 2024
Exam Conducting Body	Central Board of Secondary Education
Exam & Subject Name	Class 12 Chemistry
Category	Answer Key
Exam Date	27 February 2024
Unofficial Answer Key	27 February 2024
Official Answer Key	To be notified
Official Website	https://www.cbse.nic.in/

CBSE Class 12 Chemistry Answer Key Set 1 (56/2/1)

SECTION A
Questions no. I to 16 are Multiple Choice type Questions, carrying 1 mark each 16×1=16

1. When MnO2 is fused with KOH in air, it gives
(A) KMnO4
(B) K2MnO4
(C) MngO7
(D) Mn2O
Answer: (B) K2MnO4

2. Ligand EDTA is an example of a:
(A) Monodentate ligand
(B) Didentate ligand
(C) Tridentate ligand
(D) Polydentate ligand

Answer:(D) Polydentate ligand

3. Which of the following ligand forms chelate complex?
(A) (CO2-) 4
(B) CI
(C) NO
(D) NH3

Answer:(A) CO 4

Answer: Option C

Answer: Option (d)

Answer: Option A

7. Ethanol on heating with conc, H₂SO₄ at 413 K gives:
(A) C2H5OSO3H
(B) C₂H-O-CH3
(C) C₂H-O-C2H5
(D) CH2=CH2
Answer:(C) C₂H-O-C2H5

8. An azeotropic solution of two liquids has boiling point lower than either of them when it :
(A) is saturated
(B) shows positive deviation from Raoult’s law
(C) shows negative deviation from Raoult’s law
(D) shows no deviation from Raoult’s law
Answer:(B) shows positive deviation from Raoult’s law

9. The relative lowering of vapour pressure of an aqueous solution containing non-volatile solute is 0-0225. The mole fraction of the non-volatile solute is:
(A) 0.80
(B) 0.725
(C) 0.15
(D) 0.0225
Answer: (D) 0.0225

10. During electrolysis of aqueous solution of NaCl:
(A) H₂ (g) is liberated at cathode
(B) Na is formed at cathode
(C) O2 (g) is liberated at anode
(D) Cl2 (g) is liberated at cathode

11. The addition of catalyst during a chemical reaction alters which of the following quantities of the reaction?
(A) Enthalpy
(B) Activation energy
(C) Entropy
(D) Internal energy

Answer: (B) Activation energy

12. For the elementary reaction PQ. the rate of disappearance of ‘P’ increases by a factor of 8 upon doubling the concentration of ‘P’. The order of the reaction with respect to ‘P’ is:
(A) 3
(B) 4
(C) 2
(D) 1

Answer: (A) 3

For Questions number 13 to 16, two statements are given one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) as given below.
(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
(B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
(C) Assertion (A) is true, but Reason (R) is false.
(D) Assertion (A) is false, but Reason (R) is true.

13. Assertion (A): Aliphatic primary amines can be prepared by Gabriel phthalimide synthesis.
Reason (R): Alkyl halides undergo nucleophilic substitution with anion formed by phthalimide.

Answer:(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
14. Assertion (A): Uracil base is present in DNA.
Reason (R): DNA undergoes self-replication.

Answer: (D) Assertion (A) is false, but Reason (R) is true.
15. Assertion (A): Diazonium salts of aromatic amines are more stable than those of aliphatic amines.
Reason (R): Diazonium salts of aliphatic amines show resonance.

Answer:(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
16. Assertion (A): p-nitroaniline is a weaker base than p-toluidine.
Reason (R): The electron withdrawing effect of NO2 group in p-nitroaniline makes it a weaker base.

Answer:(A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

Chemistry Set 2 Answer Key 2024: Paper Code (56/4/2)

3. Which alkyl halide Dom the given options will undergo a reaction

Answer: Option A

4.  Which of the following stids represents Vitamin C?
(A) Banelusric acid
(B) Gluconic acid
(C) Ascorbic acid
(D) Benzoic acid

Answer: (C) Ascorbic acid
5. Hasenmund reduction is used for the preparation of Aldehydes. The estalyat used in this reaction is
Answer:  (a)

6. Consider the following reaction

Identify A and B from the given options
(A) A-Methanol. B-Potassium formate
(B) A-Ethanol. B-Potassium formate
(C) A-Methanal, 8-Ethanol
(D) A-Methanol, B-Potassium acetate

Answer: (A) A-Methanol. B-Potassium formate

11. Nucleophilic addition of Grignard reagent to ketones followed by hydrolysis with dilute acids forms:
(A) Alkene
(C) Tertiary alcohol
(B) Primary alcohol
(D) Secondary alcohol

Answer: (C) Tertiary alcohol

12. Match the reagents required for the given reactions:

Column A	Column B
1. Oxidation of primary alcohols to 2. Butan-2-one to Butan-2-ol 3. Bromination of Phenol to 2, 4, 6- 4. Dehydration of propan-2-ol to	(p) NaBH, aldehydes (q) 85% phosphoric acid at 440 K (r) Tribromophenol PCC (s) Bromine water propene

(A) 1-(г), П-(p), III-(s), IV(q)
(B) 1-(q), II(r), III-(p). IV- (9)
(C) 1-(8), II-(q). III-(p). IV(r)
(D) 1-(p). II-(s), III-(r). IV- (q)

Answer: (A) 1-(г), П-(p), III-(s), IV(q)

Chemistry Set 3 Answer Key 2024: Paper Code  (56/3/3-13)

1. Which of the following ligands is an ambidentate ligand?
(A) CO
(B) SCN-
(C) NH3
(D) H₂O

Answer: (B) SCN-

2. On adding AgNO3 solution to 1 mole of CoCl3. 4NH3, one mole of AgCl is precipitated. The secondary valency of Cois:
(A) 6
(C) 3
(B) 4
(D) 7

Answer: (A) 6

3. Which of the following elements of 3d series of transition elements has the lowest   Δ a H°?
(B) Cr
(A) Sc
(D) Zn
(C) Cu

Answer: (D) Zn

4.

Answer: Option B

5.

Answer: Option A

6. CH3-O-CH3 when treated with excess HI gives:
(A) CH3-OH + CH3-1
(B) 2CH3-OH
(C) 2CH3-I
(D) CH3-I+CH4

Answer:C) 2CH3-I

Which of the following compounds will not react with benzene sulphonyl chloride?
(A) (C2H5)3N
(B) C2H5-NH2
(C) (C2H5)2 NΗ
(D)C6H5- NH2

Answer:(A) (C2H5)3N

6. Scurvy’ is caused by a deficiency of vitamins:
(A) E
(B) A
(C) C
(D) D
Answer: (C) C

7. A 1% solution of solute ‘X’ is isotonic with a 6% solution of sucrose (molar mass = 342 g mol¹). The molar mass of solute ‘X’ is:
(A) 34-2 g mol-1
(B) 57 g mol-1
(C) 114 g mol-¹
(D) 3-42 g mol 1

10. The half life of a first order reaction with rate constant (k) of 3 min-1
(A) 0.693 min
(B) 2.31 min
(C) 6.93 min
(D) 0.231 min

Answer: (D) 0.231 min

11. Which of the following cells is used in hearing aids?
(A) Dry cell
(B) Mercury cell
(C) Nickel-cadmium cell
(D) Fuel cell
Answer: (C) Nickel-cadmium cell
12. Aniline on reaction with Bromine water gives:
(A) o-bromoaniline
(B) 2,4,6-tribromoaniline
(C) m-bromoaniline
(D) p-bromoaniline

Answer: (B) 2,4,6-tribromoaniline

13. Assertion (A): AmixH and AmixV are zero for an ideal solution.
Reason (R): The solution which obeys Raoult’s law over the entire range of concentration is called an ideal solution.
Answer: (a)

14. Assertion (A): Rate of reaction decreases with increase in temperature.
Reason (R): Number of effective collisions increases with increase in temperature.

Assertion (A): Phenol on reaction with aqueous NaOH gives sodium phenoxide.
Reason (R): This reaction supports the acidic nature of phenol.

Asertion (A): Boiling point of butan-1-ol is higher than that of butan-1-amine.
Reason (R): Being more polar, butan-1-ol intermolecular hydrogen bonds form stronger compared to as butan-1-amine.

CBSE Class 12 Chemistry Answer Key 2024 Set 1

SECTION – A (MCQs)

1. Van’t Hoff factor for K₂SO4 solution, assuming complete ionization is

(A) 1
(B) 3
(C) 13
(D) 2

Answer: (B) 3

5. The rate of a reaction increases sixteen times when the concentration of the reactant increases four times. The order of the reaction is

(A) 2.5
(B) 2.0
(C) 1.5
(D) 0.5

Answer: (B) 2.0

6. Which of the following cell is used in hearing aids?

(A) Mercury cell
(B) H2-O2 fuel cell
(C) Dry cell
(D) Ni-Cd cell

Answer: (A) Mercury cell

7. Isotonic solutions have the same

(A) density
(C) osmotic pressure
(B) refractive index
(D) volume

Answer: (C) osmotic pressure

8. Transition metals are known to make interstitial compounds. Formation of interstitial compounds makes the transition metal

(A) more hard
(C) more ductile
(B) more soft
(D) more metallic

Answer: (A) more hard

9. Auto-oxidation of chloroform in air and light produces a poisonous gas known as

(A) Phosphine
(C) Phosgene
(B) Mustard gas
(D) Tear gas

Answer: (C) Phosgene

10. Out of the following alkenes, the one which will produce tertiary butyl alcohol on acid catalysed hydration is

(A) CH3CH3CH=CH2
(B) CH3CH=CH2
(C) CH3-CH=CH-CH3
(D) (CH3)2C = CH2

Answer: (D) (CH3)2C = CH2

CBSE Class 12 Chemistry Answer key 2024 Set 3

Check out the solutions of paper code 56/5/3 section A Mcqs in the table below.

Question Number	Correct Options
1. Van’t Hoff factor for K2SO4 solution, assuming complete ionization is	(B) 3
2. Dilution affects both conductivity as well as molar conductivity. Effect of dilution on both is as follows:	(C) conductivity increases whereas molar conductivity decreases
3. Which of the following species can act as the strongest base?	(C) RO–
4. In which of the following molecules, C atom marked with asterisk is chiral?	(A) I, II, III
5. The rate of a reaction increases sixteen times when the concentration of the reactant increases four times. The order of the reaction is	(B) 2.0
6. Which of the following cell is used in hearing aids?	(A) Mercury cell
7. Isotonic solutions have the same	(C) Osmotic pressure
8. Transition metals are known to make interstitial compounds. Formation of interstitial compounds makes the transition metal	(A) more hard
9. Auto-oxidation of chloroform in air and light produces a poisonous gas known as	(C) Phosgene
10. Out of the following alkenes, the one which will produce tertiary butyl alcohol on acid catalysed hydration is	(D) (CH3)2C = CH2
11. The correct name of the given reaction is	(A) Sandmeyer’s Reaction
12. The specific sequence in which amino acids are arranged in a protein is called its	(A) Primary Structure

CBSE Class 12th Chemistry Answer key 2024 Set 1

Check out the solutions of paper code 56/1/1 section A Mcqs in the table below.

Question	Correct Option
1. Which one of the following first-row transition elements are expected to have the highest third ionization enthalpy?	(D) Vanadium (Z = 23)
2. Which of the following compounds will give a ketone on oxidation with chromic anhydride (CrO3)?	(D) CH3–CH2–(CH–OH)–CH3
3. Two of the three components of DNA are beta-D 2-deoxyribose and a heterocyclic base. The third component is:	(A) Adenine
4. For an electrolyte undergoing association in a solvent, the can’t Hoff factor	(A) is always greater than one
5. For the reaction X + 2Y → P. the differential form equation of the rate	(A) 2d[P]/dt = -d[Y]/dt
6. The compound which undergoes SN1 reaction most rapidly is	To be updated
7. Acetic acid reacts with PCl5 to give:	(C) CH3–COCl
8. The formation of cyanohydrin from an aldehyde is an example of :	(C) nucleophilic reaction
9. In the Arrhenius equation, when log k is plotted against 1/T, a straight line is obtained whose :	(D) the slope is -Ea/2.303R and intercept is log A.
10. The reaction of an alkyl halide with sodium alkoxide forming ether in known as:	(C) Williamson synthesis
11. The correct order of the ease of dehydration of the following alcohols by the action of conc. H2SO4 is:	(A) (CH3)3C–OH > (CH3)2CH–OH > CH3CH2–OH
12. Which functional groups of glucose interact to form cyclic hemiacetal leading to pyranose structure?	(A) Aldehyde group and hydroxyl group at C–4

Class 12 Chemistry Answer Key 2024 & Paper Analysis

Watch the video to get the Class 12 Chemistry Exam Analysis at the earliest.

Answer Key of Chemistry Class 12 CBSE 2024 for Set 1,2,3

Here we will provide the CBSE Class 12 Chemistry Answer key 2024 for Chemistry question sets 1, 2 and 3. A majority of students said that Section A’s Multiple Choice questions are a little bit tricky and they found some difficulties while solving these sections. Candidates can cross-check their answers with the answer key of chemistry class 12 cbse 2024 of Section A.

Class 12 Chemistry Answer Key of Section A
Question Number	QP Code: 56/3/3	QP Code: 56/5/2	QP Code: 56/2/1
1	(B) SCN–	(C) RO–	(B) K2MnO4
2	(A) 6	(C) Phosgene	(D) Polydentate ligand
3	(D) Zn	(D) Volume	(A) C2O42-
4	(B) CH2 – Cl – C6H6 –OH	(A) Primary Structure	(C) CH2 = CH – X
5	(A) C6H6 – CH2MgBr	(A) more hard	(D) Cl – C6H6 – OH
6	(C) 2CH3 – I	(D) Gatterman reaction	(A) C6H6 – OH + CH3–I
7	(A) (C2H5)3N	To be updated	(C) C2H5 – O – C2H5
8	(C) C	(B) 2	(B) shows positive deviation from Raoult’s law
9	(B) 57 g mol-1	(D) both increase	(D) 0.0225
10	(D) 0.231 min	To be updated	(A) H2 (g) is liberated at cathode
11	(B) Mercury cell	To be updated	To be updated
12	(B) 2,4,6-tribromoaniline	To be updated	To be updated
13	(A) Both A and R are true and R is the correct explanation of A	To be updated	To be updated
14	(A) Both A and R are true and R is the correct explanation of A	To be updated	To be updated
15	(A) Both A and R are true and R is the correct explanation of A	To be updated	To be updated
16	(A) Both A and R are true and R is the correct explanation of A	To be updated	To be updated
17	To be Updated.	To be Updated.	To be Updated.
18	To be Updated.	To be Updated.	To be Updated.

CBSE Class 12 Chemistry Board Question Paper 2024 PDF

The CBSE Class 12 Chemistry Exam was conducted in multiple sets at different exam centers. Students should assess the difficulty level of the Chemistry Question paper sets that differ from their own. The board question paper has a weightage of 70 points and all questions are mandatory to attempt. Students can access CBSE 12 Chemistry question papers from various sets on this page.

CBSE 12 Chemistry Board Question Paper 2024 PDF
CBSE 12th Chemistry question paper 2024 Set 1	Click here
Chemistry question paper 2024 Set 2	Click here
CBSE Class 12 Chemistry question paper 2024 Set 3	Click here

Class 12 Chemistry Question Paper Analysis 2024

After the conclusion of the Exam, we talked to the students as well as the teachers to know the difficulty level of the Paper. Let’s check the test takers’ and subject experts’ reactions on the CBSE Class 12 Chemistry Exam below.

CBSE Class 12 Chemistry Paper Analysis by Students

According to general reviews, students regarded the work to be moderate and balanced.

• The paper was NCERT-based and covered all relevant topics.
• The MCQ component of the paper was a little challenging but workable. Section B was easy.
• The long-answer questions were straightforward, if fairly lengthy.
• The short-answer questions were moderately difficult.
• Organic chemistry is frequently the most difficult component of the exam. Students rated organic chemistry this year as moderate. Expected questions regarding conversions and name reactions were posed.

CBSE Class 12th Chemistry Exam Analysis by Teachers

Experts and educators have stated that the chemistry paper was balanced and of moderate difficulty.

• The majority of the questions were direct and based on NCERT. Almost all of the students found the CBSE Class 12 Chemistry paper to be fairly average.
• The paper pattern was consistent with the CBSE sample paper.
• The majority of the paper’s questions ranged from simple to moderate, except for a couple that could have been difficult for pupils.

Class 12 Chemistry Question Paper 2024 Pattern 

With calculating the scores with the CBSE Class 12 Chemistry Answer Key 2024, students must know the Chemistry marking Scheme of Each section.  As per the CBSE Class 12 Chemistry sample paper, the CBSE Class 12 Chemistry question paper consists of Five sections. All the sections hold different marks and different types of questions. The board will ask the very short answer type, short answer type, and case-based questions in the CBSE Class 12 Chemistry Examination. Check out the detailed section-wise pattern listed below: 

1. Section A consists of 18 Questions carrying 1 mark each [Multiple Choice Questions]

2. Section B consists of 7 questions carrying 2 marks each [Very Short Answer Questions]

3. Section C consists of 5 questions carrying 3 marks each [Short Answer Questions]

4. Section D consists of 2 Questions carrying 4 marks each [Case Based Questons]

5. Section E consists of 2 Questions carrying 5 marks each [Long Answer Questions]

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CBSE Class 12 Chemistry Answer Key Set 3 Last year

1, A compound CaCl2.6h2O undergoes complete dissociation in water, The Van’t Hoff Factor ‘i’ is:

a)  9, b) 6, c)3, d) . 4

Answer: c) 3

2. For a Zero order reaction of type A →products, the rate equation may be expressed as:

Answer: Option (a)

3. Which of the following Cu 2+ halide is not known?

(a) CuBr2

(b) Cul2

(c) CuCl2

(d) CuF2

Answer: Option (b)

Q4. Which of the following structures represents a-D-glucose?

Answer: (a)

5. The compounds [Cr(H2O)lCl3, [Cr(H2O) Cl]C12. H2O and [Cr(H2O)4C12]Cl. 2H2O exhibit:

(a) Linkage isomerism
(b) Geometrical isomerism
(c) . Ionization isomerism
(d) Hydrate isomerism

Answer: (d) Hydrate isomerism

6. Which of the following alkenes on acid catalysed hydration gives a tertiary alcohol?

(a) 2-Butene

(b) 2-Methylpropene

(c) Propene

(d) 95 1-Butene

Answer: (b) 2-Methylpropene

7. When nitrobenzene is heated with tin and concentrated HCl, the product formed is:

Answer: (a)

8. The reaction of 1-phenyl-2-chloropropane with alcoholic KOH gives mainly:

(a) 1-phenylpropene

(b) 3-phenylpropene

(c) 1-phenylpropene 1-phenylpropan-3-ol

(d) 1-phenylypropan-2-ol

Answer: (a) 1-phenylpropene

9. Corrosion of iron is:

(a) a decomposition process a photochemical process
(b) a photochemical process
(c) an electrochemical process
(d) a reduction process

Answer: (a) reduction process

10. The number of molecules that react with each other in an elementary reaction is a measure of the:

(a) activation energy of the reaction
(b) order of the reaction
(c) stoichiometry of the reaction
(d) molecularity of the reaction

Answer: (d) molecularity of the reaction

11. On hydrolysis, which of the following carbohydrates gives glucose and galactose?

(a) Sucrose
(c) Maltose
(b) Lactose
(d) Cellulose

Answer: (b) Lactose

12. The deficiency of which of the following vitamins causes ‘Rickets’?

(a) Vitamin A
(b) Vitamin D
(c) Vitamin B
(d) Vitamin C

Answer; (b) Vitamin D

13. Which of the following is an ‘Acetal’?

Answer: (d)

For Questions number 15 to 18, two statements are given – one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.

(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
(c) Assertion (A) is true, but Reason (R) is false.
(d) Assertion (A) is false, but Reason (R) is true.

15. Assertion (A): When NaCl is added to water, a depression in freezing point is observed.

Reason (R): The vapour pressure of solution is increased which causes depression in freezing point.

Answer:(c) Assertion (A) is true, but Reason (R) is false.

16. Assertion (A): Monobromination of aniline can be conveniently done by protecting the amino group by acetylation.

Reason (R): Acetylation decreases the activating effect of the amino group.

Answer:(c) Assertion (A) is true, but Reason (R) is false.

Class 12 Chemistry Answer Key last Year

Section- A

• The magnetic moment of [NiCl4]2-

(a) 1.82 BM
(b) 2.82 BM
(c) 4.42 BM
(d) 5.46 BM
(Atomic no : Ni= 28)
Answer: (a) 1.82 BM

• Which of the following cell was used in Apollo space programme?

(a) Mercury Cell

(b) Daniel Cell

(c) H2-O2 Fuel cell

(d) Dry Cell

Answer: (c) H2-O2 Fuel cell

• Which one of the following has lowest pKa value?

(a) CH3-COOH

(b) O2N-CH2-COOH

(c) Cl-CH2-COOH

(d) HCOOH

Answer: (b) O2N-CH2-COOH

• Which of the following ions has the electronic configuration 3d6 ?

(a) Ni³⁺
(b) Co³⁺
(c) Mn²⁺
(d) Mn³⁺
Answer: (b) CO³⁺

• Consider the following standard electrode potential values:

Fe3+ (aq) + e- —> Fe2+ (aq) Eo = + 0.77 V
MnO4- (aq) + 8H+ + 5e- —-> Mn2+ (aq) + 4H2O (l) Eo = + 1.51V
What is the cell potential for the redox reaction?
(a) -2.28 V
(b) – 0.74 V
(c) + 0.74 V
(d) + 2.28 V
Answer: (c)  +0.74 V

4. The following experimental rate data were obtained for a reaction carried out at 25o C:

A(g) + B(g) —-> C(g) + D(g)

• A voltaic cell is made by connecting two half cells represented by half equations below:

Sn2+(aq) + 2e- –>Sn(s)Eo=-0.14 V

Fe3+(aq)+e- –> Fe2+ (aq)Eo=+0.77 V

• Which statement is correct about this voltaic cell?

(a) Fe2+ is oxidised and the voltage of the cell is -0.91 V.
(b) Sn is oxidised and the voltage of the cell is 0.91 V.
(c) Fe2+ is oxidised and the voltage of the cell is 0.91 V.
(d) Sn is oxidised and the voltage of the cell is 0.63 V.

Answer: to be updated

• What are the orders with respect to A(g) and B(g)?

Answer: To be updated

• Which of the following aqueous solution will have highest boiling point?

(a) 1.0 M KCl

(b) 1.0 M K₂SO4

(c) 2.0 M KCl

(d) 2.0 M K2SO4

Answer: to be updated

• Amides can be converted into amines by the reaction named

(a) Hoffmann degradation

(b) Ammonolysis

(c) Carbylamine

(d) Diazotisation

Answer: (a) Hoffmann degradation

• Which of the following would not be a good choice for reducing nitrobenzene to aniline?

(a) LiAlH4

(b) H2/Ni

(c) Fe and HCl

(d) Sn and HCl

Answer: (a) LiAlH₄

• Which property of transition metals enables them to behave as catalysts?

(a) High melting point

(b) High ionisation enthalpy

(c) Alloy Formation

(d) Variable oxidation states

Answer: (d) Variable oxidation states

• Which of the following statements is not true about glucose?

(a) It is an aldohexose.

(b) On heating with HI it forms n-hexane.

(c) It is present in pyranose form.

(d) It gives 2,4 DNP test.

Answer: (d) It gives 2,4 DNP test.

• Which of the following alcohols will not undergo oxidation?

(a) Butanol

(b) Butan-2-ol

(c) 2-Methylbutan-2-ol

(d) 3-Methylbutan-2-ol

Answer: (d) 3-Methylbutan-2-ol

• Four half reactions I to IV are shown below:

1.  2Cl- —> Cl2 + 2e-
2. 4OH- —-> O2 + 2H2O + 2e-
3. Na+ + e- —-> Na
4. 2H+ + 2e- —-> H2

 Which two of these reactions are most likely to occur when concentrated brine is electrolysed?

(a) I and III

(b) I and IV

(c) II and III

(d) II and IV

For the questions 15 to 18 , two statements are given – one labeled as Assertion (A) and the other labelled as Reason (R ). Select the correct answer to these questions from the codes (a), (b), (c ), and (d) as given below:

(a) Both Assertion (A) and Reason (R ) are true and (R) is the correct explanation of the Assertion (A).
(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
(c) Assertion (A) is true but Reason (R) is false.
(d) Assertion (A) is false, but Reason (R) is true.

15. Assertion (A) : Vitamin C cannot be stored in our body.

Reason (R) : Vitamin C is fat soluble and is excreted from the body in urine.
Answer: (c) Assertion (A) is true but Reason (R) is false

16. Assertion (A) : The half life of a reaction is the time in which the concentration of the reactant is reduced to one half of its initial concentration.

Reason (R) : In first order kinetics when concentration of reactant is doubled, its half life is doubled.

17. Assertion (A) : Bromination of benzoic acid gives m-bromobenzoic acid.

Reason (R) : Carboxyl group increases the electron density at the meta position.
Answer: (a) Both Assertion (A) and Reason (R ) are true and (R) is the correct explanation of the Assertion (A).

18. Assertion (A): EDTA is a hexadentate ligand.

Reason (R) : EDTA has 2 nitrogen and 4 oxygen donor atoms.
Answer: (a) Both Assertion (A) and Reason (R ) are true and (R) is the correct explanation of the Assertion (A).

CBSE Class 12 Chemistry Exam Paper Analysis – Last year

We surveyed students to find out what they thought of the CBSE Class 12 Chemistry Paper Review 2024. The overall paper was simple to moderate. The questions were straightforward, and nothing was outside of the syllabus. There were some math problems that tested students’ analytical abilities, but everything else was typical in terms of complexity.

Section A, which consisted of MCQs, was the top-scoring component of the exam, according to our subject experts. For your convenience, the answer key for the Class 12 Chemistry test is provided in the sections below.

Class 12 Chemistry Question Paper PDF of Last year

After Completion of the Exam, here we have provided the CBSE Class 12 Chemistry Question Papers Pdf of last year. Candidates may download Class 12 Chemistry Question Papers and analyze the Class 12 Chemistry Answer key to calculate their expected scores.

CBSE Class 12 Chemistry Question Papers PDF Download (Last year)

CBSE Class 12 Chemistry Question Papers Set 1

CBSE Class 12 Chemistry Question Papers Set 2

CBSE Class 12 Chemistry Question Papers Set 3

Class 12 Chemistry Answer Key- Previous Year’s Repeated Questions

Section A

Q.1: Arrange the following compounds in the increasing order of their property indicated.

i) Acetaldehyde, Benzaldehyde, Acetophenone, Acetone(Reactivity towards HCN)

Answer. Acetaldehyde<Acetone<Benzaldehyde<Acetophenone

iii) CH3CH2OH, CH3CHO, CH3COOH (Boiling point)

Answer.  CH3COOH<CH3CH2OH<CH3CHO

Q.2: In a plot of m against the square root of concentration (C12) for strong and weak electrolytes, the value of limiting molar conductivity of a weak electrolyte cannot be obtained graphically. Suggest a way to obtain this value. Also state the related law, if any.

Yes, we can do it by Kohlrausch’s law.

Kohlrausch’s law:  a statement in physical chemistry: the migration of an ion at infinite dilution is dependent on the nature of the solvent and on the potential gradient but not on the other ions present.

Q.3: Write reasons for the following statements : 

(i) Benzoic acid does not undergo Friedel-Crafts reaction.

No, benzoic acid does not undergo Friedel Craft reaction because the carboxylic group is deactivating and the Lewis acid catalyst and carboxylic group are bonded.

(ii) Oxidation of aldehydes is easier than that of ketones.

oxidation of aldenyde is easier than ketone due to presence of H-atoms linked to carbonyl group carbon which is absent in ketones.

Section B

Q.4: Write reasons for the following: 

(i) Ethylamine is soluble in water whereas aniline is insoluble. 

Ethylamine when added to water forms intermolecular H−bonds with water. Hence it is soluble in water. But aniline Can form H−bonding with water to a very small extent due to the presence of a large hydrophobic −C6H5 group. Hence aniline is insoluble in water.

(ii) Amino group is o- and p-directing in aromatic electrophilic substitution reactions, but aniline on nitration gives a substantial amount of m-nitroaniline. 

Nitration is carried out in an acidic medium. In an acidic medium, aniline is protonated to give anilinium ion (which is meta-directing).

For this reason, aniline on nitration gives a substantial amount of m-nitroaniline.

(iii) Amines behave as nucleophiles.

A nucleophile is a substance that is attracted to, and then attacks, a positive or slightly positive part of another molecule or ion. All amines contain an active lone pair of electrons on the very electronegative nitrogen atom. It is these electrons that are attracted to positive parts of other molecules or ions.

OR 

b) How will you carry out the following conversions:

i) Nitrobenzene to Aniline 

Nitrobenzene is reduced to aniline by Sn and concentrated HCl. Instead of Sn, Zn or Fe also can be used. Aniline salt is given from this reaction. Then aqueous NaOH is added to the aniline salt to get released aniline. This reaction is called nitrobenzene reduction.

• Benzene is a clear, colourless, highly flammable and volatile, liquid compound.
• Aniline is a yellowish to brownish oily liquid with a musty fishy odour organic compound.

ii) Ethanamide to Methanamine

React ethanamine with nitrous acid to form an azo compound, which further reacts with water to form ethanol, which on oxidising gives ethanoic acid. After treating with an excess of ammonia the ethanoic acid becomes ethanamide, which on further reacting with Bomine and a strong base (Hoffmann bromamide degradation reaction) to form methenamine.

iii) Ethanenitrile to Ethanamine 

it’s simple
reduction of nitriles with lithium aluminium hydride or catalytic hydrogenation produce primary amines. the reaction is

CH3C≡N + H2/Ni OR LiAlH4 →  CH3CH2NH2

Q.5(a)(i) Write the electronic configuration of d5 on the basis of crystal field splitting theory if Δ0 < P.

When Δo < P, it is weak field and high spin situation’. As a result one electron entered in eg orbital and 3 electrons in t2g.

(ii) [Fe(CN)6]³- is weakly paramagnetic whereas [Fe(CN)6]4- is diamagnetic. Give reason to support this statement [Atomic no. Fe = 26].

In both and , Fe exists in the +3 oxidation state i.e., in d⁵ configuration.

Since CN⁻ is a strong field ligand, it causes the pairing of unpaired electrons. Therefore, there is only one unpaired electron left in the d-orbital.

Therefore,

On the other hand, H₂O is a weak field ligand. Therefore, it cannot cause the pairing of electrons. This means that the number of unpaired electrons is 5.

Therefore,

Thus, it is evident that is strongly paramagnetic, while is weakly paramagnetic.

(iii) Write the number of ions produced from the complex [Co(NH3)6]C12 in solution. 

The given complex can be written as [Co(NH3)6]Cl2. Thus, [Co(NH3)6]+ along with two Cl− ions are produced.

OR

Q.(b)(i) Calculate the spin only magnetic moment of the complex [CoF613-. (Atomic no. of Co = 27)

Given ion is M2+ with the atomic no. 27.

Q.6 (i) Which ion amongst the following is colourless and why?

Ti4+, Cr3+, V3+

(Atomic number of Ti = 22, Cr = 24, V = 23)

Ti is colourless because it is having no unpaired e−e- for excitation to higher energy level and it is colourless.

(ii) Why is Mn²+ much more resistant than Fe²+ towards oxidation?

Mn2+ is much more resistant than Fe2+ towards oxidationAs Mn2+ has stable configuration hence it is resistant towards oxidation. while in Fe2+ electronic configuration is 3d6 so it can lose one electron to give stable configuration 3d5.

(iii) Highest oxidation state of a metal is shown in its oxide or fluoride only. Justify the statement.

The highest oxidation state of a metal is exhibited in its oxide or fluoride only. This is because fluorine (F) and oxygen (O)are the most electronegative elements and the highest oxidation state shown by any transition element is +8.

Q.7 A compound ‘A’ (C2H4O) on oxidation gives ‘B’ (C2H4O2). ‘A’ undergoes an Iodoform reaction to give yellow precipitate and reacts with HCN to form the compound ‘C’. ‘C’ on hydrolysis gives 2-hydroxypropanoic acid. Identify the compounds ‘A’, ‘B’ and ‘C’. Write down equations for the reactions involved. 

Q.9(a) Write equations involved in the following reactions :

(i) Ethanamine reacts with acetyl chloride.

(ii) Aniline reacts with bromine water at room temperature. 

(iii) Aniline reacts with chloroform and ethanolic potassium hydroxide.

When aniline reacts with chloroform and alcoholic $KOH$ it gives an offensive smelling liquid i.e., phenyl isocyanide as product. It is called as isocyanide test. It is given by aliphatic and aromatic primary amines.

Q.9 (b)  (i) Write the IUPAC name for the following organic compound:  (CH3CH2)2NCH3

(CH3​CH2​)2​NCH3​ it is a tertiary amine, and the parent chain is ethanamine. IUPAC name is N – Ethyl – N- methyl ethanamine.

(ii) Write the equations for the following: 

(I) Gabriel phthalimide synthesis

Gabriel Phthalimide Synthesis Mechanism has 3 steps. The Synthesis is used to get primary amines from primary alkyl halides and is named after the German scientist Siegmund Gabriel.

The reaction has been generalized for applications in the alkylation of sulfonamides and imides & their deprotection in order to obtain amines. Alkylation of ammonia is quite inefficient, therefore it is substituted with phthalimide anion in the Gabriel synthesis.

(II) Hoffmann bromamide degradation 

When an amide is treated with bromine in an aqueous or ethanolic solution of sodium hydroxide, degradation of amide takes place leading to the formation of primary amine. This reaction involving degradation of amide and is popularly known as Hoffmann bromamide degradation reaction. The primary amine thus formed contains one carbon less than the number of carbon atoms in that amide.

RCONH₂ +Br₂ + 4NaOH

R-NH₂ + Na₂CO₃ + 2NaBr + 2H₂O

Q.11(a) i) Silver atom has completely filled d-orbitals in its ground state, it is still considered to be a transition element. Justify the statement. 

Silver (Ag) belongs to group 11 of d-block and its ground state electronic configuration is 4d10 5s1. It shows an oxidation state of +2 in its compounds like AgO and AgF2 in which its electronic configuration is d9 so it is a transition element.

ii) Why are E° values of Mn and Zn more negative than expected? 

Negative E° values of Mn2+ and Zn2+ are because of the stabilities of half-filled (3d5 : Mn2+)and fullyfilled (3d10 : Zn2+) configuration respectively. Ni2+ ion has higher E°  value due to highest negative enthalpy of hydration.

iii) Why do transition metals form alloys?

Transition metals have very similar atomic sizes. One metal can easily replace the other metal from its lattice to form solid solution (alloy). Transition metals are miscible with one another in the molten state. The molten state solution of two or more transition metals on cooling forms alloy.

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