CBSE Class 12 Chemistry Question Papers and Answer Key 2023

CBSE Board Class 12th Chemistry Paper Answer Key 2023

CBSE Board hasn’t released the 2023 class 12 Chemistry question paper or answer key yet. However, you can check out the genuine question paper and CBSE Class 12 Chemistry answer key 2023 here. The official consensus of the paper was moderately difficult.

CBSE Class 12 Chemistry 2023 Answer Key

Section- A

1. 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

2. 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

3. 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)

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

Answer: To be updated

5. 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

6. Which of the following ions has the electronic configuration 3d6 ?

(a) Ni³⁺

(b) Co³⁺

(c) Mn²⁺

(d) Mn³⁺

Answer: (b) CO³⁺

7. 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

8. 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

9. Amides can be converted into amines by the reaction named

(a) Hoffmann degradation

(b) Ammonolysis

(c) Carbylamine

(d) Diazotisation

Answer: (a) Hoffmann degradation

10. 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.

11. 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

12. 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

Answer: 

13. 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

14. 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

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.

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

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).

19. (a) Which of the following species cannot act as a ligand? Give reason.

OH-, NH+4, CH3NH2, H20

Answer: NH4+ ion cannot act as a ligand as it does not possess any lone pair of electrons which it can donate to central metal ion. Therefore, it does not form complexes.

(b) The complex [Co(NH3)5(NO2)]Cl2 is red in colour. Give IUPAC name of its linkage isomer.

Answer: The complex [Co(NH3)5(NO2)]Cl2 is obtained in red colour when the nitrite ligand is bound through oxygen.

IUPAC name of its linkage isomer is – Pentamminenitrocobalt(III) chloride.

20. For the pair phenol and cyclohexanol, answer the following:

(a) Why is phenol more acidic than cyclohexanol?

(b) Give one chemical test to distinguish between the two.

Answer:

(a)  Phenol is more acidic than cyclohexanol  because the phenoxide ion is more stable than the alkoxide ion. Phenoxide ion is stabilised by resonance whereas no resonance structures are possible for alkoxide ion of cyclohexanol.

(b) Bromine water test can be used to distinguish between phenol and cyclohexanol. Phenol decolorises bromine water and gives white ppt. of 2, 4, 6- tribromophenol. But cyclohexanol does not give this test.

21. (a) (i) Draw the zwitter ion structure for sulphanilic acid.

(ii) How can the activating effect of -NH2 group in aniline be controlled?

Answer:

(a) (i) Zwitter ion structure for sulphanilic acid:

(ii) The activating effect of −NH2 group can be controlled by acetylation of  −NH2 group.