Class 12 ISC Chemistry Question Paper 2023

Maximum Marks: 70

Time Allowed: Three hours

(Candidates are allowed additional 15 minutes for only reading the paper.
They must NOT start writing during this time).

This paper is divided into four sections – A, B, C and D.

Answer all questions.

Section A consists of one question having sub-parts of one mark each.

Section B consists of seven questions of two marks each.

Section C consists of nine questions of three marks each, and

Section D consists of three questions of five marks each

. Internal choices have been provided in two questions each in Section B, Section C and Section D.

The intended marks for questions are given in brackets [ ].

All working, including rough work, should be done on the same sheet as and adjacent to the rest of the answer.

Answers to sub parts of the same question must be given in one place only.

A list of useful physical constants is given at the end of this paper.

A simple scientific calculator without a programmable memory may be used for calculations.

Class 12 ISC Chemistry Question Paper 2023

Section-A

Question 1

(i) The primary alcohols are easily oxidised first into ....... and then into ......

Solution

(ii) The intermediate activated complex in a chemical reaction is highly ...... due to ....... energy.

Solution

(iii) The coordination number and oxidation state of the complex K4[Fe(CN)6] are ........ and ....... respectively.

Solution

(iv) Propanone on reaction with zinc-amalgam in presence of conc. HCl gives ........ and the reaction is known as ...... reduction.

Solution

(B) Select and write the correct alternative from the choices given below:

(i) The reaction of a primary amine with chloroform and ethanolic KOH is called: (a) Carbylamine reaction (b) Kolbe's reaction (c) Reimer-Tiemann reaction (d) Wurtz-Fittig reaction

Solution

(ii) Which one of the following statements is TRUE for the Galvanic cell? (a) Electrons flow from copper electrode to zinc electrode. (b) Current flows from zinc electrode to copper electrode. (c) Cations move towards copper electrode. (d) Cations move towards zinc electrode.

Solution

(iii) Which one of the following compounds is diamagnetic and colourless? (a) K₂Cr₂O, (b) ZnSO4 (c) KMnO4 (d) Cr2(SO4)3

Solution

(iv) For a first order reaction, the half-life period (ts) is: (a) proportional to the initial concentration. (b) inversely proportional to the initial concentration. (c) proportional to the square root of the initial concentration. (d) independent of the initial concentration.

Solution

(C) Match the following:

Solution

Solution

Solution

Section-B

Question 2

Calculate the mass of ascorbic acid (molecular mass = 176 g/mol) that should be dissolved in 155g of acetic acid to cause a depression of freezing point by 1.15K. Assume that ascorbic acid does not dissociate or associate in the solution. (Kf for acetic acid = 3.9K kg/mol)

Solution

Question 3

Give a reason for the following: (i) Cu+2 salts are paramagnetic while Cu+ salts are diamagnetic. (i) Mn+2 compounds are more stable than Fe+2 compounds.

Solution

Question 4

Give chemical equations for each of the following: (i) Ethyl chloride is treated with aqueous KOH solution. (ii) Chlorobenzene is treated with ammonia at 573K and high pressure.

Solution

Question 5

State one reason for each of the following: (i) Alkylamine is soluble in water whereas arylamine is insoluble in water. (ii) Methylamine is a stronger base than methyl alcohol.

Solution

Question 6

Calculate the emf of the following cell at 298K.

Solution

Question 7

Complete and balance the following chemical equations:

Solution

Question 8

Solution

Question 9

The osmotic pressure of blood at 37°C is 8:21 atm. How much glucose in grams should be used per litre of aqueous solution for an intravenous injection so that it is isotonic with blood? (Molecular wt of glucose 180g/mol)

Solution

Question 10

Solution

Question 11

State a reason for each of the following: (i) La(OH)3 is more basic than Lu(OH). (ii) Transition elements and their compounds act as catalyst.

Solution

Section-C

Question 12

20% of a first order reaction is completed in five minutes. How much time will the 60% reaction take to complete? Calculate the half-life period (t½) for the above reaction.

Solution

Question 13

Write the balanced chemical equations for the following name reactions: (i) Sandmeyer's reaction (ii) Wurtz reaction (iii) Finkelstein reaction

Solution

Question 14

(i) Give an example each of reducing sugar and non-reducing sugar. (ii) What is denaturation of proteins? (iii) Give an example each of water soluble vitamin and fat soluble vitamin.

Solution

Question 15

Solution

Question 16

Account for the following: (i) Phenol is a stronger acid than aliphatic alcohols. (ii) Ethanol gives iodoform reaction whereas methanol does not give iodoform reaction (iii) Ethers should not be distilled to dryness.

Solution

Question 17

(i) Identify the compounds [A], [B] and [C] in the following reactions: OR How will the following be converted? (Give chemical equation) (a) Ethyl bromide to ethyl isocyanide. (b) Aniline to benzene diazonium chloride. (c) Benzene diazonium chloride to phenol.

Solution

Question 18

A first order reaction is 50% completed in 40 minutes at 300K and in 20 minutes at 320K Calculate the activation energy of the reaction.

Solution

Section-D

Question 19

(i) Write the chemical equations to illustrate the following name reactions: (a) Cannizzaro's reaction (b) HVZ reaction (c) Aldol condensation (ii) How will the following be converted? (Give chemical equation) (a) Acetaldehyde to acetone (b) Formaldehyde to urotropine

Solution

Question 20

(i) Name the type of isomerism exhibited by the following pairs of compounds. (ii) Write the IUPAC names of the following complexes: (a) [Co(NH3)4(H2O)2]Cl3 (b) K2[Ni(CN)4]

(iii) The coordination number and oxidation state of the complex K₄[Fe(CN)₆] are ........ and ....... respectively.

(i) The reaction of a primary amine with chloroform and ethanolic KOH is called:

(a) Carbylamine reaction
(b) Kolbe's reaction
(c) Reimer-Tiemann reaction
(d) Wurtz-Fittig reaction

(ii) Which one of the following statements is TRUE for the Galvanic cell?

(a) Electrons flow from copper electrode to zinc electrode.
(b) Current flows from zinc electrode to copper electrode.
(c) Cations move towards copper electrode.
(d) Cations move towards zinc electrode.

(iii) Which one of the following compounds is diamagnetic and colourless?

(a) K₂Cr₂O,
(b) ZnSO₄
(c) KMnO4
(d) Cr₂(SO₄)₃

(iv) For a first order reaction, the half-life period (ts) is:

(a) proportional to the initial concentration.
(b) inversely proportional to the initial concentration.
(c) proportional to the square root of the initial concentration.
(d) independent of the initial concentration.

Calculate the mass of ascorbic acid (molecular mass = 176 g/mol) that should be dissolved in 155g of acetic acid to cause a depression of freezing point by 1.15K. Assume that ascorbic acid does not dissociate or associate in the solution.

(K_f for acetic acid = 3.9K kg/mol)

Give a reason for the following:

(i) Cu⁺² salts are paramagnetic while Cu⁺ salts are diamagnetic.
(i) Mn⁺² compounds are more stable than Fe⁺² compounds.

Give chemical equations for each of the following:

(i) Ethyl chloride is treated with aqueous KOH solution.

(ii) Chlorobenzene is treated with ammonia at 573K and high pressure.

State one reason for each of the following:

(i) Alkylamine is soluble in water whereas arylamine is insoluble in water.
(ii) Methylamine is a stronger base than methyl alcohol.

State a reason for each of the following:

(i) La(OH)₃ is more basic than Lu(OH).
(ii) Transition elements and their compounds act as catalyst.

Write the balanced chemical equations for the following name reactions:

(i) Sandmeyer's reaction
(ii) Wurtz reaction
(iii) Finkelstein reaction

(i) Give an example each of reducing sugar and non-reducing sugar.

(ii) What is denaturation of proteins?

(iii) Give an example each of water soluble vitamin and fat soluble vitamin.

Account for the following:

(i) Phenol is a stronger acid than aliphatic alcohols.
(ii) Ethanol gives iodoform reaction whereas methanol does not give iodoform reaction
(iii) Ethers should not be distilled to dryness.

(i) Identify the compounds [A], [B] and [C] in the following reactions:

OR

How will the following be converted? (Give chemical equation)

(a) Ethyl bromide to ethyl isocyanide.
(b) Aniline to benzene diazonium chloride.
(c) Benzene diazonium chloride to phenol.

(i) Write the chemical equations to illustrate the following name reactions:

(a) Cannizzaro's reaction
(b) HVZ reaction
(c) Aldol condensation

(ii) How will the following be converted? (Give chemical equation)

(a) Acetaldehyde to acetone
(b) Formaldehyde to urotropine

(i) Name the type of isomerism exhibited by the following pairs of compounds.

(ii) Write the IUPAC names of the following complexes:

(a) [Co(NH₃)₄(H₂O)₂]Cl₃
(b) K₂[Ni(CN)₄]