CBSE Class 12 Chemistry Chemical Kinetics MCQs Set H

Question. The rate constant of a first order reaction is 6.9×10^-3s^-1 .How much time will it take to reduce the initial concentration to its 1/8th value?
(a) 100 s
(b) 200 s
(c) 300 s
(d) 400 s
Answer: c

Question. t _1/4 can be taken as the time taken for the concentration of a reactant to drop to 3/4 of its initial value. If the rate constant for a first order reaction is k, the t _1/4 can be written as
(a) 0.75/k
(b) 0.69/k
(c) 0.29/k
(d) 0.10/k
Answer: c

Question. In Arrhenius plot, intercept is equal to
(a) -E_a/R
(b) ln A
(c) ln k
(b) log₁₀a
Answer: b

Question. Chemical kinetics is a study to find out
(a) the feasibility of a chemical reaction
(b) extent to which a reaction will proceed
(c) speed of a reaction
(d) All of the above
Answer: c

Question. For the reaction A + 2B → C, rate is given by R = [A] [B]² then the order of the reaction is
(a) 3
(b) 6
(c) 5
(d) 7
Answer: b

Question. Point out the wrong statement:
For a first order reaction
(a) time for half-change (t_1/2) is independent of initial concentration
(b) change in the concentration unit does not change the rate constant (k)
(c) time for half-change × rate constant = 0.693
(d) the unit of k is mole^–1 min^–1
Answer: d

Question. In a reaction A → Products, when start is made from 8.0 × 10^–2 M of A, half-life is found to be 120 minute. For the initial concentration 4.0 × 10^–2 M, the half-life of the reaction
becomes 240 minute. The order of the reaction is :
(a) zero
(b) one
(c) two
(d) 0.5
Answer: c

Question. 3A → B + C, it would be a zero order reaction when
(a) the rate of reaction is proportional to square of concentration of A
(b) the rate of reaction remains same at any concentration of A
(c) the rate remains unchanged at any concentration of B and C
(d) the rate of reaction doubles if concentration of B is increased to double
Answer: b

 Question. In terms of the ‘Collision Theory of Chemical Kinetics’, the rate of a chemical reaction is proportional to
(a) the change in free energy per second
(b) the change in temperature per second
(c) the number of collisions per second
(d) the number of products molecules
Answer: c

Question. Order of reaction can be
(a) 0
(b) fraction
(c) whole number
(d) integer, fraction, zero
Answer: d

Question. In a slow reaction, rate of reaction generally ………. with time:
(a) decreases
(b) increases
(c) sometimes increases and sometimes decreases.
(d) remains constant
Answer: a

 Question. In the Arrhenius plot of ln k vs 1/T, a linear plot is obtained with a slope of –2 × 10⁴ K. The energy of activation of the reaction (in kJ mole^–1) is (R value is 8.3 J K^–1 mol^–1)
(a) 83
(b) 166
(c) 249
(d) 332
Answer: b

Question. For the following reaction: NO₂(g) + CO(g) → NO(g) + CO₂(g), the rate law is: Rate = k [NO₂]². If 0.1 mole of gaseous carbon monoxide is added at constant temperature to the reaction mixture which of the following statements is true?
(a) Both k and the reaction rate remain the same
(b) Both k and the reaction rate increase
(c) Both k and the reaction rate decrease
(d) Only k increases, the reaction rate remain the same
Answer: a

Question. For the following homogeneous reaction,
A + B k→ C
the unit of rate constant is
(a) sec^–1
(b) sec^–1 mol L^–1
(c) sec^–1 mol^–1 L
(d) sec^–1 mol^–2 L²
Answer: c

Question. In a reaction, when the concentration of reactant is increased two times, the increase in rate of reaction was four times.
Order of reaction is :
(a) zero
(b) 1
(c) 2
(d) 3
Answer: c

Question.In the rate equation, when the conc. of reactants is unity then rate is equal to
(a) specific rate constant
(b) average rate constant
(c) instantaneous rate constant
(d) None of above
Answer: a

 Question. A zero order reaction is one whose rate is independent of
(a) the concentration of the reactants
(b) the temperature of reaction
(c) the concentration of the product
(d) the material of the vessel in which reaction is carried out
Answer: a

Question. If the rate of the reaction is equal to the rate constant, the order of the reaction is
(a) 3
(b) 0
(c) 1
(d) 2
Answer: b

Question. Which one of the following reactions is a true first order reaction?
(a) Alkaline hydrolysis of ethyl acetate
(b) Acid catalyst hydrolysis of ethyl acetate
(c) Decomposition of N₂O
(d) Decomposition of gaseous ammonia on a hot platinum surface
Answer: c

Question. The term – dc/dt in a rate equation refers to :
(a) the conc. of a reactant
(b) the decrease in conc. of the reactant with time
(c) the velocity constant of reaction
(d) None of these
Answer: b

Question. At the beginning the decrease in the conc. of reactants is
(a) slow
(b) moderate
(c) rapid
(d) None of above
Answer c

Question. The rate law for the reaction
xA + yB → mP + nQ is Rate = k [A]^c[B]^d. What is the total order of the reaction?
(a) (x + y)
(b) (m + n)
(c) (c + d)
(d) x/y
Answer: c

Question. The rate law for the single- step reaction 2A+ B→2C, is given by:
(a) rate = k [A].[B]
(b) rate = k [A]².[B]
(c) rate = k [2A].[B]
(d) rate = k [A]².[B]o
Answer: b

Question. Rate of a reaction can be defined as
(a) the rate of decrease in concentration of any one of the reactants
(b) the rate of increase in concentration of any one of the products
(c) the rate of decrease in concentration of any one of the reactants or the rate of increase in concentration of any one of the products
(d) the sum of rate of decrease in concentration of all the reactants or the rate of increase in concentration of all the products
Answer: c

Question. The average rate and instantaneous rate of a reaction are equal
(a) at the start
(b) at the end
(c) in the middle
(d) when two rate have time interval equal to zero
Answer: d

Question. The half-life of a reaction is inversely proportional to the square of the initial concentration of the reactant. Then the order of the reaction is
(a) 0
(b) 1
(c) 2
(d) 3
Answer: d

Question. The reaction A→ B follows first order kinetics. The time taken for 0.8 mole of A to produce 0.6 mole of B is 1 hour.What is the time taken for conversion of 0.9 mole of A to produce 0.675 mole of B?
(a) 2 hours
(b) 1 hour
(c) 0.5 hour
(d) 0.25 hour
Answer: b

Question. The rate constant for the reaction
2N₂O₅ → 4NO₂ + O₂ is 3.10 × 10^–5 sec^–1. If the rate is 2.4 × 10^–5 mol litre^–1 sec^–1 then the concentration of N₂O₅ (in mol litre^–1) is :
(a) 0.04
(b) 0.8
(c) 0.07
(d) 1.4
Answer: b

Question. What is the activation energy for a reaction if its rate doubles when the temperature is raised from 20°C to 35°C? (R = 8.314 J mol^–1 K^–1)
(a) 269 kJ mol^–1
(b) 34.7 kJ mol^–1
(c) 15.1 kJ mol^–1
(d) 342 kJ mol^–1
Answer: b

Question. Collision theory is applicable to
(a) first order reactions
(b) zero order reactions
(c) bimolecular reactions
(d) intra-molecular reactions
Answer: c

Question. Instantaneous rate of a chemical reaction is
(a) rate of reaction in the beginning
(b) rate of reaction at the end
(c) rate of reaction at a given instant
(d) rate of reaction between two specific time intervals
Answer: c

Question. The activation energy for a reaction is 9.0 kcal/mol. The increase in the rate constant when its temperature is increased from 298K to 308K is
(a) 63%
(b) 50%
(c) 100%
(d) 10%
Answer: a

Question. The rate of reaction between two specific time intervals is called
(a) instantaneous rate
(b) average rate
(c) specific rate
(d) ordinary rate
Answer: b

Question. The rate of reaction
(a) increases as the reaction proceeds
(b) decreases as the reaction proceeds
(c) remains the same as the reaction proceeds
(d) may decrease or increase as the reaction proceeds
Answer: d

Question. According to the collision theory of reaction rates, the rate of reaction increases with temperature due to
(a) greater number of collision
(b) higher velocity of reacting molecules
(c) greater number of molecules having the activation energy
(d) decrease in the activation energy 
Answer: a

 Question. A catalyst
(a) increases the rate of reaction by decreasing ΔG of a reaction.
(b) increases the rate of reaction by increasing ΔG of a reaction.
(c) increases the rate of reaction by decreasing activation energy of the forward reaction.
(d) increases the rate of reaction by providing an alternative pathway via an intermediate with lower activation energy.
Answer: d

Question. The rate of reaction depends upon the
(a) volume
(b) force
(c) pressure
(d) conc. of reactants
Answer: d

Question. The plot of concentration of the reactant vs time for a reaction is a straight line with a negative slope. The reaction follows a rate equation
(a) zero order
(b) first order
(c) second order
(d) third order
Answer: a

Question. The rate of a chemical reaction tells us about,
(a) the reactants taking part in reaction
(b) the products formed in the reaction
(c) how slow or fast the reaction is taking place
(d) None of the above
Answer: c

Question. Which one of the following statements for the order of a reaction is incorrect ?
(a) Order can be determined only experimentally.
(b) Order is not influenced by stoichiometric coefficient of the reactants.
(c) Order of reaction is sum of power to the concentration terms of reactants to express the rate of reaction.
(d) Order of reaction is always whole number.
Answer: d

Question. The order of a reaction with rate equal to k[A]^3/2 [B]^–1/2 is :
(a) 1
(b) -1/2
(c) -3/2
(d) 2
Answer: a

Question. Which of the following reaction does not occur fastly ?
(a) Precipitation of AgCl by mixing aqueous solutions of AgNO₃ and NaCl.
(b) Burning of gasoline
(c) Rusting of iron
(d) Burning of LPG for cooking
Answer: c

Question. The unit of rate of reaction is
(a) mole/dm³
(b) mole/pound
(c) mole/dm³ sec
(d) mole/cm³
Answer: c

Question. The rate of the reaction 2NO+ Cl₂ → 2NOCl is given by the rate equation rate = k [NO]² [Cl₂]
The value of the rate constant can be increased by:
(a) increasing the concentration of NO.
(b) increasing the temperature.
(c) increasing the concentration of the Cl₂
(d) doing all of the above
Answer: b

Question. Units of rate constant of first and zero order reactions in terms of molarity M unit are respectively
(a) sec^–1, Msec^–1
(b) sec^–1, M
(c) Msec^–1, sec^–1
(d) M, sec^–1.
Answer: a

Question. A reaction involving two different reactants can never be
(a) bimolecular reaction
(b) second order reaction
(c) first order reaction
(d) unimolecular reaction
Answer: d

Question. In the reaction 2A + B → A2B, if the concentration of A is doubled and that of B is halved, then the rate of the reaction will:
(a) increase 2 times
(b) increase 4 times
(c) decrease 2 times
(d) remain the same
Answer: a

Question. In the Haber process for the manufacture of ammonia the following catalyst is used
(a) Platinized asbestos
(b) Iron with molybdenum as promoter
(c) Copper oxide
(d) Alumina
Answer: b

Question. If the rate of a gaseous reaction is independent of pressure, the order of reaction is:
(a) 0
(b) 1
(c) 2
(d) 3
Answer: a

Question. The rate of reaction is doubled for every 10°C rise in temperature. The increase in reaction rate as a result of temperature rise from 10°C to 100°C is
(a) 112
(b) 512
(c) 400
(d) 614
Answer: b

Question. Half life of a first order reaction is 4s and the initial concentration of the reactant is 0.12 M. The concentration of the reactant left after 16 s is
(a) 0.0075 M
(b) 0.06 M
(c) 0.03 M
(d) 0.015 M
Answer: a

Question. Rate of which reaction increases with temperature :
(a) of any type of reactions
(b) of exothemic reactions
(c) of endothemic reactions
(d) of none
Answer: a

Question. The rate constant of a reaction is 3.00 × 10³ L mol^–1 sec^–1.The order of this reaction will be:
(a) 0
(b) 1
(c) 2
(d) 3
Answer: c

Question. In respect of the equation k = Ae^{-E_a / RT} in chemical kinetics, which one of the following statements is correct ?
(a) A is adsorption factor
(b) E_a is energy of activation
(c) R is Rydberg’s constant
(d) k is equilibrium constant
Answer: b

Question. The rate of a first order reaction is 1.5 × 10^–2 mol L^–1 min^–1 at 0.5 M concentration of the reactant. The half life of the reaction is
(a) 0.383 min
(b) 23.1 min
(c) 8.73 min
(d) 7.53 min
Answer: b