KENDRIYA VIDYALAYA NO.

1 ROORKEE
SAMPLE PAPER 2024-25
CLASS: XII
CHEMISTRY (043)
Max. Marks: 70 Time: 3 Hrs
General Instructions:
a) There are 33 questions in this question paper with internal choice.
b) Section A consists of 16 multiple-choice questions carrying 1 mark each.
c) Section B consists of 5 very short answer questions carrying 2 marks each.
d) Section C consists of 7 short answer questions carrying 3 marks each.
e) Section D consists of 2 case-based questions carrying 4 marks each.
f) Section E consists of 3 long answer questions carrying 5 marks each.
g) All questions are compulsory.
h) Use of log tables and calculators is not allowed
Q SECTION A
No The following questions are multiple-choice questions with one correct answer. Each question
carries 1 mark. There is no internal choice in this section.
1. CH3CH2CH2Br + NaCN → CH3CH2CH2CN + NaBr, will be fastest in
(a) ethanol (b) methanol (c) N, N dimethyl formamide (d) Water

2. The inversion of configuration of optically active alkyl halides occurs in 1M

a.
SN1 nucleophilic substitution reaction b) SN2 electrophilic substitution reaction
c) SN2 nucleophilic substitution reaction d) SN1 electrophilic substitution reaction
3. Which among the following is a false statement?
(a) Rate of zero order reaction is independent of initial concentration of reactant.
(b) Half life of a third order reaction is inversely proportional to square of initial concentration of the reactant.
c) Molecularity of a reaction may be zero or fraction.
(d) For a first order reaction, t1/2=0.693K

4. For the reaction N2 + 3H2 → 2NH3 if Δ[NH3]Δt = 2 × 10-4 mol L-1s-1, the value of −Δ[H2]Δt would be
(a) 1 × 10-4 mol L-1s-1
(b) 3 × 10-4 mol L-1s-1
(c) 4 × 10-4 mol L-1s-1
(d) 6 × 10-4 mol L-1s-1
5. For a first order reaction, the rate constant is found to be 2 x 10-3s-1. The half-life of the reaction is
1M
a. 30 s b) 300 s c) 220 s d) 347 s

6 a. The compound which contains all the four 1°, 2°, 3° and 4° carbon atoms is
(a) 2, 3-dimethyl pentane (b) 3-chloro-2, 3-dimethylpentane
(c) 2, 3, 4-trimethylpentane (d) 3, 3-dimethylpentane

7 For a chemical reaction A→B, it is found that the rate of reaction doubles when the concentration of A is
increased four times. The order of reaction is
(a) Two (b) One (c) Half (d) Zero
8. b. The rate of a certain hypothetical reaction
A + B + C → products
is given by r = −d[A]dtK[A]1/2[B]1/3[C]1/4. The order of the reaction is
(a) 13/11
(b) 13/14
(c) 12/13
(d) 13/12
9. a. Which of the following are arranged in the decreasing order of dipole moment?
(a) CH3Cl, CH3Br, CH2F (b) CH3Cl, CH3F, CH3Br
(c) CH3Br, CH3Cl, CH3F (d) CH3Br, CH3F, CH3Cl

10. a.
Fora reaction x + y → z, rate ∝ |X|. What is (i) moleculariiy and (ii) order of reaction?
(a) (i)2, (ii) 1 (b) (i)2,(ii) 2 (c) (i) 1, (ii) 1 (d) (i) 1, (ii) 2

11. The intercept and slope of the following diagram (a plot between ln k and 1/T) 1M
are

a.
ln A, -Ea/R b) A, -k c) ln A, -Ea/2.303 R d) A, -Ea/R
12 Which of the following compounds can yield only one monochlorinated
product upon free radical chlorination?
a. (a) 2, 2-Dimethylpropane (b) 2-Methylpropane (c) 2-Methylbutane (d) n-
Butane
Given below are two statements labelled as Assertion (A) and Reason (R).Choose the correct
option
a. Both A and R are true and R is the correct explanation of A
b. Both A and R are true but R is not the correct explanation of A.
c. A is true but R is false.
d. A is false but R is true.

13. Assertion(A): Aromatic primary amines can be prepared by Gabriel phthalimide synthesis.
Reason (R): Aryl halides undergo nucleophilic substitution with anion formed by phthalimide.
Select the most appropriate answer from the options given below:
 14 Assertion : Molecularity greater than three is not observed.
Reason : The overall molecularity of complex reaction is equal to molecularity of the slowest
step.

15 Assertion: It is difficult to replace chlorine by -OH in chlorobenzene in comparison to that in

chloroethane.
Reason: Chlorine-Carbon(C-Cl) bond in chlorobenzene has partial
double bond character due to resonance.:

16 Assertion: Increase in concentration of reactant will not change the rate for a zero-
order reaction.
Reason: Rate constant for a zero-order reaction is a constant for a particular initial
concentration.

SECTION B
This section contains 5 questions with internal choice in one question. The following questions
are very short answer type and carry 2 marks each.

17. A first order reaction takes 40 min for 30% decomposition. What will be t 12?

18. a) Out of CH3CH2CH2Cl and CH2=CH–CH2–Cl, which one is more reactive towards SN1 reaction?
b) Write one stereochemical difference between SN1 and SN2 reactions.

19 Define the following :

(i) Order of a reaction
(ii) Activation energy of a reaction
20 a) State a condition under which a bimolecular reaction is kinetically first order reaction.
b) Define pseudounimolecular reaction with an example.
21 a. Name the suitable alcohol and reagent, from which 2-Chloro-2-methyl propane can be prepared.
b) What is an ambident nucleophile ? Give one example.

SECTION C
This section contains 7 questions with internal choice in one question. The following questions
are short answer type and carry 3 marks each.
22
 2 For a chemical reaction variation in concentration, [R] v/s time(min.) plot shown below
3

I. What is the order of reaction?

II. What are the units of rate constant for the reaction?
III. If initial conc. of the reactant is half of the original conc. how will t1/2 change?
Draw a plot of log [R]0/[R] v/s time (s)
2 In a reaction between A and B the initial rate of reaction (r 0) was measured for different initial
4 concentrations of A and B as Given below
A/molL 0.20 0.20 0.40
B/mol L 0.30 0.10 0.05
r0/mol L 5.07x10-5 5.07x10-5 1.43x10-4

What is the order of reaction with respect to A & B?

2 Give reason :
5 (a) p-dicholorobenzene has higher melting point than that of ortho or meta isomer.
(b) Haloarenes are less reactive towards SN reactions.
(c) Grignard reagents are prepared under anhydrous conditions.

26
Identify A,B,C and D

a. Which of the products will be a major product in the reaction given below? Explain.

2 The following compounds are given to you : 2-Bromopentane, 2-Bromo-2-methylbutane, 1-Bromopentane

7. (a) Write the compound which is most reactive towards SN2 reaction.
(b) Write the compound which is optically active.
(c) Write the compound which is most reactive towards β-elimination reaction

2 Write the products:

8

:
 SECTION D
The following questions are case-based questions. Each question has an internal choice and
carries 4 (1+1+2) marks each. Read the passage carefully and answer the questions that follow

2 The substitution reaction of alkyl halide mainly occurs by SN1 or SN2 mechanism. Whatever mechanism
9 alkyl halides follow for the substitution reaction to occur, the polarity of the carbon halogen bond is
responsible for these substitution reactions. The rate of SN1 reactions are governed by the stability of
carbocation whereas for SN2 reactions steric factor is the deciding factor. If the starting material is a chiral
compound, we may end up with an inverted product or racemic mixture depending upon the type of
mechanism followed by alkyl halide
. 1. Predict the stereochemistry of the product formed if an optically active alkyl halide undergoes
substitution reaction by SN2 mechanism
. 2. Name the instrument used for measuring the angle by which the plane polarised light is rotated.
or
(±)2-Butanol is optically inactive.explain.
3) Define the following terms : (i) Enantiomers (ii) Racemic mixture
3 Zero order reactions are relatively uncommon but they occur under special conditions. Some enzyme
0 catalysed reactions and reactions which occurs on metal surfaces are a few examples of zero order
reactions. The decomposition of gaseous ammonia on a hot platinum surface is a zero order reaction at
high pressure.At high pressure, the metal surface gets saturated with gas molecules. So a further change
in reaction conditions is unable to alter the amount of ammonia on the surface of the catalyst making
the rate of the reaction independent of its concentration.
1) If [R]0 and [R] are the concentrations of the reactant initially and after time t, give the equation
relating k.

2 ) Draw the graph between concentration of reaction vs time in a zero order reaction.

3) For a reaction: 2NH2 g) Pt N2( g) + 3H2(g)

Rate = k
(i) Write the order and molecularity of this reaction.
(ii) Write the unit of k.

SECTION E
The following questions are long answer type and carry 5 marks each. All questions have an
internal choice.

3 a) How can the following conversions be carried out:

1 (i) Aniline to bromobenzene (ii) Chlorobenzene to 2-chloroactophenone (iii) Chloroethane to butane
b) RX with KCN gives cyanides but with AgCN forms isocyanides.Explain.
c)Write the major product

H-Br

a) If the rate constant of a reaction is k = 3 × 10-4 s-1, then identify the order of the reaction.
(b) Rate constant k for a first order reaction has been found to be 2.54 × 10-3 sec-1. Calculate its 3/4th
life, (log 4 = 0.6020)
c)The rate constant for the first order decomposition of H2O2 is given by the following equation:
log k = 14.2 – 1.0×104TK
Calculate Ea for this reaction

Following data are obtained for the reaction:

N2O5 → 2NO2 + 12O2
t/s 0 300 600

[N205]/mol L-1 1.6 × 10-2 0.8 × 10-2 0.4 × 10-2

(a) Show that it follows first order reaction.

(b) Calculate the half-life.
(Given log 2 = 0.3010 log 4 = 0.6021)

(b) What is the physical significance of energy of activation ? Explain with diagram.

(c) In some cases it is found that a large number of colliding molecules have energy more than threshold
energy, yet the reaction is slow. Why?
26. b.

27.

28. a.

SECTION D
The following questions are case-based questions. Each question has an internal choice and
carries 4 (1+1+2) marks each. Read the passage carefully and answer the questions that
follow.
29.
30. (i)

31. . The rate constants of a reaction at 200K and 500K are 0.02s–1 and 0.20s–1 respectively. Calculate the
value of Ea (Given 2.303R = 19.15 JK -1mol-1)
(i)

32. a) Give reason for the following

(i) aryl halides are less reactive towards nucleophilic substitution reaction.
(ii) Thionyl chloride method is preferred for preparing alkyl chloride from alcohol.
(b) Write the major product

H-Br

Write use for each of the following.

(i) DDT (ii) Iodoform
33. Attempt any five of the following 5M

a. Why is Cr2+ reducing and Mn3+ oxidising when both have d4 configuration?
b. Calculate the magnetic moment of a divalent ion in aqueous solution if its atomic number is 25
c. How does the acidified permanganate solution react with iron (II) ions
d. Describe the preparation of potassium dichromate from Na2CrO4
e. What is the oxidation state of Chromium in Chromate and dichromate ion?
f. Ti+3 is coloured while Sc+3 is colourless in aqueous solution
g. Actinoids show wide range of oxidation states. Why?

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