CBSE Class 12 Chemistry Compartment Question Paper 2023 with Answer Key (Set 1 - 56/C/1)

Choose the compound which is more acidic than phenol:

• (A) \( o-nitrophenol \)
• (B) ethanol
• (C) \( o-methylphenol \)
• (D) \( o-methoxyphenol \)

Which of the following reactions is a halogenated exchange reaction:

• (A) \( Alkene + HX \longrightarrow Alkane with halogen \)
• (B) \( R{-}X + NaI \xrightarrow{Dry acetone} R{-}I + NaX \)
• (C) \( R{-}OH + HCl \xrightarrow{ZnCl_2} R{-}Cl + H_2O \)
• (D) Bromination of toluene with \( Br_2 \) and \( Fe \) in dark

The most common oxidation state for all lanthanoids is:

• (A) \( +5 \)
• (B) \( +2 \)
• (C) \( +3 \)
• (D) \( +4 \)

A reaction follows second order kinetics. How is the rate of reaction affected if the concentration of the reactant is reduced to half? Choose the correct value from the following:

• (A) four times
• (B) eight times
• (C) \( \frac{1}{4} \) of the original value
• (D) three times

Solutions of two electrolytes X and Y are diluted. Molar conductivity of X increases 25 times whereas that of Y increases 1.5 times. Which one is a stronger electrolyte?

• (A) X
• (B) Y
• (C) Both X and Y
• (D) None of the above

Unit of rate constant for the zero order reaction is:

• (A) \( s^{-1} \)
• (B) \( mol^{-1} L\, s^{-1} \)
• (C) \( mol^{-2} L^{2} s^{-1} \)
• (D) \( mol\, L^{-1} s^{-1} \)

Three compounds are given below:


The correct decreasing order of their basic strength is:

• (A) II \(>\) III \(>\) I
• (B) III \(>\) II \(>\) I
• (C) III \(>\) I \(>\) II
• (D) I \(>\) III \(>\) II

Which type of isomerism is shown by the complexes \([Co(NH_3)_5Br]SO_4\) and \([Co(NH_3)_5SO_4]Br\) ?

• (A) Linkage
• (B) Ionisation
• (C) Optical
• (D) Solvate

What would be the major product of the given reaction?
\[ HCHO + CH_3MgI \xrightarrow{H_2O} \; ? \]

• (A) Ethanal
• (B) Propanol
• (C) Ethanol
• (D) Propanal

Pentan-2-one and Pentan-3-one can be distinguished by:

• (A) Fehling’s test
• (B) Sodium bicarbonate test
• (C) Tollens’ test
• (D) Iodoform test

Hoffmann Bromamide Degradation reaction is given by:

• (A) Nitrobenzene
• (B) Benzamide
• (C) Methyl cyanide
• (D) Propanamide

Given below is the decomposition of hydrogen peroxide in alkaline medium, which is catalysed by iodide ions:
\[ 2H_2O_2 \xrightarrow{I^-, \; alkaline medium} 2H_2O + O_2 \]

The above reaction takes place in two steps:


Step I: \( H_2O_2 + I^- \longrightarrow H_2O + IO^- \) (slow)

Step II: \( H_2O_2 + IO^- \longrightarrow H_2O + I^- + O_2 \)


Molecularity of Step I and Step II is:

• (A) Step I – 2, Step II – 2
• (B) Step I – 1, Step II – 2
• (C) Step I – 2, Step II – 1
• (D) Step I – 3, Step II – 1

Oxidation state of central metal atom in the given complex is:
\[ [Co(NH_3)_4(H_2O)_2]Cl_3 \]

• (A) \( +2 \)
• (B) \( +3 \)
• (C) \( +1 \)
• (D) \( +4 \)

A galvanic cell can behave as an electrolytic cell when:

• (A) \( E_{cell} = E_{ext} \)
• (B) \( E_{cell} > E_{ext} \)
• (C) \( E_{cell} = 0 \)
• (D) \( E_{ext} > E_{cell} \)

Assertion (A): Phenol gives 2,4,6-trinitrophenol on treatment with concentrated \( HNO_3 \) and concentrated \( H_2SO_4 \).


Reason (R): –OH group in phenol is \( m \)-directing.

• (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.

Assertion (A): D (+)-Glucose is dextrorotatory.


Reason (R): Symbol ‘D’ represents its dextrorotatory nature.

• (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.

Assertion (A): Zn, Cd and Hg are not regarded as transition elements.


Reason (R): Zn, Cd and Hg do not have partially filled d-orbitals in their ground state or in any one of their common oxidation states.

• (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.

Assertion (A): Benzene diazonium salt is stable and can be easily stored.


Reason (R): Benzene diazonium chloride decomposes easily.

• (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.

The rate of a reaction quadruples when the temperature changes from 293 K to 313 K. Calculate the energy of activation of the reaction, assuming that it does not change with temperature.
\[ (\log 2 = 0.30,\; \log 4 = 0.60) \quad [R = 8.314\; J\, K^{-1}\, mol^{-1}] \]

(b)i) Why do amino acids show amphoteric behaviour?

(b)(ii) What happens when D-Glucose is treated with hydroxylamine?

(i) Write the structure of 1-chloro-4-ethylcyclohexane.

(ii) Why is sulphuric acid not used during the reactions of alcohols with KI?

(i) Arrange the following in increasing order of their boiling points:

1-chloropropane, 2-chloropropane, 1-chlorobutane


(A) 2-chloropropane \(<\) 1-chloropropane \(<\) 1-chlorobutane

(ii) What is an ambident nucleophile? Give one example.

(a) Why is \([Ti(H_2O)_6]^{3+}\) coloured?

(b) Write IUPAC name of the given complex: \( K_3[Cr(C_2O_4)_3] \)

(a) Why are iron pipes usually coated with zinc?

(b) Why does mercury cell give a constant voltage throughout its life?

(a) Write the mathematical relation between rate constant and half-life period of a zero order reaction.

(b) Define Pseudo first order reaction with an example.

(a) Why is \( pK_a \) of ClCH\textsubscript{2COOH lower than the \( pK_a \) of CH\textsubscript{3COOH?

(b) Write the chemical equation for Hell-Volhard-Zelinsky reaction.

Write the chemical equation for the following:

(a) Hydration of propene in presence of an acid

(b) Reaction between Ethyl bromide and C\textsubscript{2H\textsubscript{5ONa

(c) Reaction between Dimethyl ether and Hydrogen iodide

Using valence bond theory, predict:

(a) Hybridisation of central metal atom of the complex \([Co(NH_3)_6]^{3+}\)

(b) Its shape and magnetic behaviour

(c) Whether it is a high spin or a low spin complex

[Atomic number: \(CO\) = 27]

Give reasons for the following:

(a) Reduction with iron scrap and HCl is preferred for the preparation of amines from nitro compounds.


(b) Lower aliphatic amines are soluble in water.


(c) Pyridine is used in the acylation reaction of amines.


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

(i) Why do tertiary alkyl halides undergo S\textsubscript{N}1 reaction at a faster rate?

(ii) Define Enantiomers.

(iii) Why is chloroform stored in dark coloured air tight bottles?

(i) Write the major alkene that would be formed by dehydrohalogenation of 2-Bromopentane.

(ii) Which would undergo S\textsubscript{N}2 reaction at a faster rate and why?

Given compounds:

Compound A: CH\textsubscript{3–CH\textsubscript{2–Br

Compound B: \quad
\begin{tabular{c
CH\textsubscript{3

\quad|

CH\textsubscript{3–C–Br

\quad|

CH\textsubscript{3

\end{tabular

(iii) Why is chlorobenzene less reactive towards nucleophilic substitution reaction?

(a) Name the linkage which connects monosaccharide units in polysaccharides.

(b) Carbohydrates are classified on the basis of their behaviour on hydrolysis. Write the hydrolysis products of sucrose.

(c) Write two differences between Amylose and Amylopectin.

What are reducing sugars?

Sucrose is dextrorotatory but the mixture obtained after hydrolysis is laevorotatory. Why?

(a) 20 mL of a liquid A was mixed with 20 mL of liquid B. The volume of resulting solution was found to be less than 40 mL. What do you conclude from the above data?

(b) Which of the following show positive deviation from Raoult’s law?

Carbon disulphide and Acetone;

Phenol and Aniline;

Ethanol and Acetone

(c) The vapour pressure of a solution of glucose in water is 750 mm Hg at 100°C. Calculate the mole fraction of solute.

(Vapour pressure of water at 373 K = 760 mm Hg)

The boiling point of solution increases when 1 mol of NaCl is added to 1 litre of water while addition of 1 mol of methanol to one litre of water decreases its boiling point. Explain the above observations.

(i) A cell and its emf is given below:

Pt (s) \(\mid\) H\(_2\)(g, 1 bar) \(\mid\) H\(^+\)(aq, 1 M) \(\parallel\) Cu\(^{2+}\)(aq, 1 M) \(\mid\) Cu (s)

emf of the cell = +0.34 V

Write the reduction half-reaction at cathode.

How is standard Gibbs energy for a reaction related to equilibrium constant?

Calculate emf of the given cell:

Mg(s) \(\mid\) Mg\(^{2+}\)(0.1 M) \(\parallel\) Cu\(^{2+}\)(1.0 × 10\(^{-3}\) M) \(\mid\) Cu(s)


Given:
\(E^\circ_{Cu^{2+}/Cu} = +0.34\) V, \quad \(E^\circ_{Mg^{2+}/Mg} = -2.37\) V

(log 100 = 2)

State Kohlrausch’s law of independent migration of ions.

How much electricity in terms of Faraday is required to produce 40 g of Al from molten Al\(_2\)O\(_3\)?

(Given: Atomic mass of Al = 27 u)

Calculate log \(K_c\) for the following reaction at 298 K:

Zn(s) + Cu\(^{2+}\)(aq) \(\rightleftharpoons\) Zn\(^{2+}\)(aq) + Cu(s)


Given:
\(E^\circ_{Zn^{2+}/Zn} = -0.76 \, V\), \quad \(E^\circ_{Cu^{2+}/Cu} = +0.34 \, V\)

(a) Compound A undergoes Rosenmund reduction to give compound B with molecular formula C\textsubscript{7}H\textsubscript{6}O. Compound B does not give Fehling’s test but reacts with conc. NaOH to give C and D.

Identify A, B, C and D and write all the reactions involved.

Write one chemical test to distinguish between compound B and propanone.

Compound A with molecular formula (C\textsubscript{2}H\textsubscript{6}O) on oxidation by PCC gives compound B, which on treatment with dilute alkali forms compound C (a β-hydroxy aldehyde). B on oxidation by potassium permanganate forms C.

Identify A, B, C and D and write all the chemical equations involved.

The chemistry of the actinoids is more complex as compared to the lanthanoids. Why?

Why is E\textdegree{} for Mn\textsuperscript{3+}/Mn\textsuperscript{2+} redox couple more positive?

Why do transition metals form large numbers of complex compounds?

How does acidified potassium permanganate solution react with Fe\textsuperscript{2+} ions? Write ionic equation.

Calculate the ‘spin only’ magnetic moment of a divalent ion of a metal M in aqueous solution. The atomic number of the metal M is 25.