Class 12 Chemistry Chapter 4 Chemical Kinetics MCQs | Class 12 Chemistry Chapter 4 Chemical Kinetics Objective Type Questions and Answers
Questions
1
The rate constant of a reaction depends upon
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?
Answer:3
3
Fora reaction x + y → z, rate ∝ |X|. What is (i) moleculariiy and (ii) order of reaction?
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
2H2 + 2NO → 2H2O + N2
which has rate = K|H2||NO|², is
Answer:mol-2 L² s-1
5
Which of the following, is an example of a fractional order reaction?
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?
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?
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 ?
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
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.
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
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
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
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
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?
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
(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
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
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)
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
Reason: rate constant also doubles
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
Answer: First order
Chapters
