Class 12 Chemistry Chapter 4 Chemical Kinetics MCQs | Class 12 Chemistry Chapter 4 Chemical Kinetics Objective Type Questions and Answers

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Questions
1 The rate constant of a reaction depends upon
A temperature of the reaction
B extent of the reaction
C initial concentration of the reactants
D the time of completion of reaction

Answer:the time of completion of reaction
2 For a reaction nx – y → z the rate of reaction becomes twenty seven times when the concentration of X is increased three times. What is the order of the reaction?
A 2
B 1
C 0
D 3

Answer:3
3 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

Answer: (i)2, (ii)1
4 The unit of rate constant for the reaction
2H2 + 2NO → 2H2O + N2
which has rate = K|H2||NO|², is
A mol L-1 s-1
B s-1
C mol-2 L² s-1
D mol L-1

Answer:mol-2 L² s-1
5 Which of the following, is an example of a fractional order reaction?
A NH4NO2 → N2 + 2H2O
B NO + O3 → NO2 + O2
C 2NO + Br2 → 2NOBr
D CH3CHO → CH4 + CO

Answer: CH3CHO → CH4 + CO
6 A reaction in which reactants (R) are converted into products (P) follows second order kinetics. If concentration of R is increased by four times, what will be the increase in the rate of formation of P?
A 9 times
B 4 times
C 16 times
D 8 times

Answer:16 times
7 The decomposition of dimethyl ether is a fractional order reaction. The rate is given by rate =k(PCH3OCH3)3/2. If the pressure is measured in bar and time in minutes, then what are the units of rate and rate constant?
A bar min-1, bar2 min-1
B bar min-1, bar1/2 min-1
C bar1/2 min-1, bar2 min-1
D bar min-1, bar1/2 min-1

Answer:bar min-1, bar1/2 min-1
8 In a reaction, 2X → Y, the concentration of X decreases from 0.50 M to 0.38 M in 10 min. What is the rate of reaction in Ms-1 during this interval ?
A 2 × 10-4
B 4 × 10-2
C 2 × 10-2
D 1 × 10-2

Answer:2 × 10-4
9 If the rate of a reaction is expressed by, rate = A [A]² [B], the order of reaction will be
A 2
B 3
C 1
D 0

Answer: 3
10 For a first order reaction A → B the rate constant is x min−1 . If the initial concentration of A is 0.01M , the concentration of A after one hour is given by the expression.
A 0.01 e−x
B 1 x10-2 (1-e-60x)
C (1x10-2) e-60x
D none of these

Answer: (1x10-2) e-60x
11 A zero order reaction X →Product , with an initial concentration 0.02M has a half life of 10 min. if one starts with concentration 0.04M, then the half life is
A 10 s
B 5 min
C 20 min
D Cannot be predicted using the given information

Answer: 20 min
12 For a first order reaction A → product with initial concentration x mol L−1 , has a half life period of 2.5 hours . For the same reaction with initial concentration (x/2) mol L−1 the half life is
A (2.5 × 2) hours
B (2.5 / 2) hours
C 2.5 hours
D Without knowing the rate constant, t1/2 cannot be determined from the given data

Answer: Without knowing the rate constant, t1/2 cannot be determined from the given data
13 The decomposition of phosphine (PH3) on tungsten at low pressure is a first order reaction. It is because the
A rate is proportional to the surface coverage
B rate is inversely proportional to the surface coverage
C rate is independent of the surface coverage
D rate of decomposition is slow

Answer: rate is independent of the surface coverage
14 For a reaction Rate = k[acetone]3/2 acetone then unit of rate constant and rate of reaction respectively is
A (mol L-1s-1), (mol-1/2 L1/2 s-1)
B (mol-1/2 L1/2s-1), (mol L-1 s-1)
C (mol1/2 L1/2s-1), (mol L-1 s-1)
D (mol Ls-1), (mol1/2 L1/2 s-1)

Answer:(mol-1/2 L1/2s-1), (mol L-1 s-1)
15 The addition of a catalyst during a chemical reaction alters which of the following quantities?
A Enthalpy
B Activation energy
C Entropy
D Internal energy

Answer:Activation energy
16 Consider the following statements :
(i) increase in concentration of the reactant increases the rate of a zero order reaction.
(ii) rate constant k is equal to collision frequency A if Ea = 0
(iii) rate constant k is equal to collision frequency A if Ea = °
(iv) a plot of ln(k) vs T is a straight line
(v) a plot of ln (k) vs 1/T is a straight line with a positive slope.
Correct statements are
A (ii) only
B (ii) and (iv)
C (ii) and (v)
D (i), (ii) and (v)

Answer: (ii) only
17 In a reversible reaction, the enthalpy change and the activation energy in the forward direction are respectively −x kJ mol−1 and y kJ mol−1 . Therefore , the energy of activation in the backward direction is
A ( y −x ) kJ mol−1
B ( x + y )J mol−1
C ( x −y ) kJ mol−1
D ( x + y ) × 103 J mol−1

Answer:( x + y ) × 103 J mol−1
18 What is the activation energy for a reaction if its rate doubles when the temperature is raised from 200K to 400K? (R = 8.314 JK-1mol-1)
A 234.65 kJ mol−1K−1
B 434.65 kJ mol−1K−1
C 334.65 J mol−1K−1
D 434.65 J mol−1K−1

Answer: 434.65 J mol−1K−1
19 Assertion: rate of reaction doubles when the concentration of the reactant is doubles if it is a first order reaction.
Reason: rate constant also doubles
A Both assertion and reason are true and reason is the correct explanation of assertion
B Both assertion and reason are true but reason is not the correct explanation of assertion
C Assertion is true but reason is false
D Both assertion and reason are false

Answer: Assertion is true but reason is false
20 The rate constant of a reaction is 5.8 × 10−2 s−1 . The order of the reaction is
A First order
B zero order
C Second order
D Third order

Answer: First order

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