CBSE Class 12 Chemistry Question Paper 2024 (Set 1 - 56/1/1) with Answer Key

Which one of the following first row transition elements is expected to have the highest third ionization enthalpy?

• (A) Iron (Z = 26)
• (B) Manganese (Z = 25)
• (C) Chromium (Z = 24)
• (D) Vanadium (Z = 23)

Which of the following compounds will give a ketone on oxidation with chromic anhydride (CrO3)?

Correct Answer: (D)

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Two among the three components of DNA are \(\beta\)-D-2-deoxyribose and a heterocyclic base. The third component is:

• (A) Adenine
• (B) Phosphoric acid
• (C) Sulphuric acid
• (D) Uracil

For an electrolyte undergoing association in a solvent, the van’t Hoff factor:

• (A) is always greater than one
• (B) has negative value
• (C) has zero value
• (D) is always less than one

For the reaction X + 2Y → P, the differential form equation of the rate law is:

• (A) 2d[P]/dt = -d[Y]/dt
• (B) -d[P]/dt = -d[X]/dt
• (C) +d[X]/dt = -d[P]/dt
• (D) -2d[Y]/dt = +d[P]/dt

The compound which undergoes SN1 reaction most rapidly is:

• (A)
• (B)
• (C)
• (D)

Correct Answer: (A)

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Acetic acid reacts with PCl5 to give:

• (A) Cl – CH2 – COCl
• (B) Cl – CH2 – COOH
• (C) CH3 – COCl
• (D) CCl3 – COOH

The formation of cyanohydrin from an aldehyde is an example of:

• (A) nucleophilic addition
• (B) electrophilic addition
• (C) nucleophilic substitution
• (D) electrophilic substitution

In the Arrhenius equation, when log k is plotted against 1/T, a straight line is obtained whose:

• (A) slope is \(\frac{A}{R}\) and intercept is \(E_a\)
• (B) slope is \(A\) and intercept is \(\frac{-E_a}{R}\)
• (C) slope is \(\frac{-E_a}{RT}\) and intercept is log A
• (D) slope is \(\frac{-E_a}{2.303R}\) and intercept is log A

The reaction of an alkyl halide with sodium alkoxide forming ether is known as:

• (A) Wurtz reaction
• (B) Reimer-Tiemann reaction
• (C) Williamson synthesis
• (D) Kolbe reaction

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
• (B) (CH3)2CH – OH > CH3CH2 – OH > (CH3)3C – OH
• (C) CH3CH2 – OH > (CH3)2CH – OH > (CH3)3C – OH
• (D) (CH3)2CH – OH > (CH3)3C – OH > CH3CH2 – OH

Which functional groups of glucose interact to form cyclic hemiacetal leading to pyranose structure?

• (A) Aldehyde group and hydroxyl group at C – 4
• (B) Aldehyde group and hydroxyl group at C – 5
• (C) Ketone group and hydroxyl group at C – 4
• (D) Ketone group and hydroxyl group at C – 5

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

Reason (R): NaCl undergoes dissociation in water.

Assertion (A): Separation of Zr and Hf is difficult.

Reason (R): Zr and Hf have similar radii due to lanthanoid contraction.

Assertion (A): The pK\textsubscript{a of ethanoic acid is lower than that of C1 – CH2 – COOH.

Reason (R): Chlorine shows electron withdrawing (–I) effect which increases the acidic character of C1 – CH2 – COOH.

Assertion (A): Aniline is a stronger base than ammonia.

Reason (R): The unshared electron pair on nitrogen atom in aniline becomes less available for protonation due to resonance.

Calculate the potential of Iron electrode in which the concentration of Fe\textsuperscript{2+} ion is 0.01 M.

Given \( E^{\circ}_{Fe^{2+}/Fe} = -0.45 \, V at 298 K \)

[Given: log 10 = 1]

Define molecularity of the reaction. State any one condition in which a bimolecular reaction may be kinetically first order.

What happens when D-glucose is treated with the following reagents?

• (a) HI
• (b) Conc. HNO3

Draw the structures of major monohalo products in each of the following reactions:

Write the chemical equation when:

(a) Butan-2-one is treated with Zn(Hg) and conc. HCl.

(b) Two molecules of benzaldehyde are treated with conc. NaOH.

When a certain conductivity cell was filled with 0.05 M KCl solution, it has a resistance of 100 ohms at 25°C. When the same cell was filled with 0.02 M \(AgNO_{3}\) solution, the resistance was 90 ohms. Calculate the conductivity and molar conductivity of \(AgNO_{3}\) solution.

Given:
Conductivity of 0.05 M KCl solution = \( 1.35 \times 10^{-2}\, \Omega^{-1}\, cm^{-1}\)

The following initial rate data were obtained for the reaction: \[ 2NO (g) + Br_2 (g) \rightarrow 2 NOBr (g) \]




(a) What is the order with respect to NO and \(Br_{2}\) in the reaction?

(b) Calculate the rate constant (k).

(c) Determine the rate of reaction when the concentrations of NO and \(Br_{2}\) are 0.4 M and 0.2 M, respectively.

(a) Write the formula for the following coordination compound:
Potassium tetrahydroxidozincate (II)

(b) Arrange the following complexes in the increasing order of conductivity of their solution: \[ [Cr(NH_3)_5Cl] Cl_2, \, [Cr(NH_3)_3Cl_3], \, [Cr(NH_3)_6Cl_3] \]

(c) Identify the type of isomerism exhibited by the following complexes:

• (i) \( [Co(NH_3)_5NO_2]^{2+} \)
  (ii) \( [Co(en)_3]Cl_3 \)

(a) Which of the following is an allylic halide?


(i)

(ii)

(b) Out of chlorobenzene and 2,4,6-trinitrochlorobenzene, which is more reactive towards nucleophilic substitution and why?

(c) Which isomer of C4H9Cl has the lowest boiling point?

(a) Write the mechanism of the following reaction: \[ CH_3CH_2OH \xrightarrow{H^+ \, 443\, K} CH_2 = CH_2 \]

(b) Write the main product in each of the following reactions:

Answer the following: (any three)


(a) What is peptide linkage?

(c)  Which one of the following is a polysaccharide? Sucrose, Glucose, Starch, Fructose

(d) Give one example each for water-soluble vitamins and fat-soluble vitamins.

Compound (A) \( \left( C_6H_{12}O_2 \right) \) on reduction with LiAlH\textsubscript{4 gives two compounds (B) and (C). The compound (B) on oxidation with PCC gives compound (D) which upon treatment with dilute NaOH and subsequent heating gives compound (E). Compound (E) on catalytic hydrogenation gives compound (C). The compound (D) is oxidized further to give compound (F) which is found to be a monobasic acid (Molecular weight = 60). Identify the compounds (A), (B), (C), (D), (E) and (F).

(a) What is crystal field splitting energy?

(b) Give reason for the violet colour of the complex \( [Ti(H_2O)_6]^{3+} \) on the basis of crystal field theory.

(a) \( [Cr(NH_3)_6]^{3+} \) is paramagnetic while \( [Ni(CN)_4]^{2-} \) is diamagnetic. Explain why.

(b) Explain why \( [Fe(CN)_6]^{3-} \) is an inner orbital complex, whereas \( [Fe(H_2O)_6]^{3+} \) is an outer orbital complex.

(i) At the same temperature, \( CO_2 \) gas is more soluble in water than \( O_2 \) gas. Which one of them will have a higher value of \( K_H \) and why?

(ii) How does the size of blood cells change when placed in an aqueous solution containing more than 0.9% (mass/volume) sodium chloride?

(iii) 1 molal aqueous solution of an electrolyte \( A_2B_3 \) is 60% ionized. Calculate the boiling point of the solution.

(ii) Define colligative property. Which colligative property is preferred for the molar mass determination of macromolecules?

Question 32 (a):

N,N-diethylbenzenesulphonamide is insoluble in alkali. Give reason.

(b) Aniline does not undergo Friedel-Crafts reaction. Why?

(d) Write the chemical reaction involved in Gabriel phthalimide synthesis.

(e) How will you convert aniline to p-bromoaniline?

(f) Complete the following reaction:
\[ C_6H_5N_2^+Cl^- \xrightarrow{(i) HBF_4} \xrightarrow{(ii) NaNO_2/Cu, \Delta} \quad ? \]

(g) Write the structures of A and B in the following reaction:
\[ C_6H_5COOH \xrightarrow{NH_3, \Delta} A \xrightarrow{Br_2/NaOH} B \]

(i) The melting and boiling points of Zn, Cd, and Hg are low.

(ii) Of the \( d^4 \) species, Cr\(^{2+}\) is strongly reducing while Mn\(^{3+}\) is strongly oxidizing.

(iii) \( E^0 \) value of Cu\(^{2+}\)/Cu is \( +0.34 \) V.

(b) Complete and balance the following chemical equations: