MCQs Chemical Kinetics for ISC Class 12 Questions with Answers

MCQs Chemical Kinetics for ISC Class 12 Questions with Answers. These MCQ  / Objective Type Questions is based on latest reduced syllabus according 2021-22 session on bifurcated pattern. Main motto of MCQ Type Question is cracking the next upcoming Sem-2 exam of council. Visit official website CISCE for detail information about ISC  Class-12 Chemistry

MCQs Chemical Kinetics for ISC Class 12 Questions with Answers

Board	ISC
Class	12th (XII)
Subject	Chemistry
Chapter	Chemical Kinetics
Syllabus	on bifurcated syllabus (after reduction)
Session	2021-22
Bifurcated	Sem-2
Topic	MCQ / Objective Type Question

MCQs Chemical Kinetics for ISC Class 12 Questions with Answers

Question 1. In the following reaction, how is the rate of appearance of the underlined product related to the rate of disappearance of the underlined reactant?

BrO−3 (aq) + 5 Br^– +6H⁺ → 3 Br₂ (1) + 3H₂O (l)
(a) 𝑑[𝐵𝑟2]/𝑑𝑡 = -d [Br^–]/dt
(b) 𝑑[𝐵𝑟2]/𝑑𝑡 = 35 𝑑[𝐵𝑟−]/𝑑𝑡
(c) d [Br₂]/dt = 35 d [Br^–]/dt
(d) 𝑑[𝐵𝑟2]/𝑑𝑡 = –53 d [Br^–]/dt

Ans:–(c) d [Br₂]/dt = 35 d [Br^–]/dt

Question 2 The rate constant for the reaction 2N₂O₅ → 4NO₂ + O₂ is 3.0 × 10^-5 sec^-1. If the rate is 2.40 × 10^-5 mol litre^-1 sec^-1, then the concentration of N₂O₅ (in mol litre^-1) is:
(a) 1.4
(b) 1.2
(c) 0.04
(d) 0.8

Ans :-(d) 0.8

Question 3 For the reaction A + B → C + D, doubling the concentration ofboth the reactants increases the reaction rate by 8 times and doubling the concentration of only B simply doubles the reaction rate. The rate law is given as
(a) r = k[A]¹² [B]¹²
(b) r = k [A] [B]²
(c) r – k [A]² [B]
(d) r = k [A] [B]

Ans :–(c) r – k [A]² [B]

Question 4 In a first order reaction, the concentration of the reactant decreases from 800 mol/dm³ to 50 mol/dm³ in 2 × 10⁴ sec. The rate constant
for the reaction in sec^-1
(a) 2 × 10⁴
(b) 3.45 × 10^-5
(c) 1.386 × 10^-4
(d) 2 × 10^-4

Ans :–(c) 1.386 × 10^-4

Question 5 For reaction aA → xP, when [A] = 2.2 mM the rate was found to be 2.4 mMs^-1. On reducing the concentration of A to half, the rate changes to 0.6 mMs^-1. The order of reaction with respect to A is
(a) 1.5
(b) 2.0
(c) 2.5
(d) 3.0

Ans : –(b) 2.0

Question 6  The rate equation for the reaction 2A + B → C is found to be: rate = k [A] [B]. The correct statement inxelation to this reaction is that the
(a) unit of R must be s^-1
(b) t_1/2 is constant
(c) rate of formation of C is twice the rate of disappearance of A.
(d) value of k is independent of the initial concentration of A and B.

Ans :-(d) value of k is independent of the initial concentration of A and B.

Question 7 A + 2B → C + D. If- d [A]/dt = 5 × 10^-4 mol L^-1 s^-1, Then – 𝑑[𝐵]𝑑𝑡is
(a) 2.5 × 10^-4 mol L^-1 s^-1
(b) 5.0 × 10^-4 mol L^-1 s^-1
(c) 2.5 × 10^-3 mol L^-1 s^-1
(d) 1.0 × 10^-3 mol L^-1 s^-1

Ans:- (d) 1.0 × 10^-3 mol L^-1 s^-1

Question 8 For a certain reaction aA → bB, the rate of reaction is doubled when the concentration of A is increased by four times. The rate ot reaction is equal to
(a) k[A]^a
(b) k[A]^1/2
(c) k[A]^1/a
(d) k[A].

Ans :-(b) k[A]^1/2

Question 9 For which of the following reactions, the temperature coefficient is maximum?
(a) A → B : E_a = 50 kJ
(b) P → Q : E_a = 40 kj
(c) X → Y : E_a = 60kJ
(d) W → Z : E_a = 80kJ

Ans :–(d) W → Z : E_a = 80kJ

Question 10 A zero order reaction A → Products, has rate constant 10^-2 mole L^-1 s^-1. If a process is started with 10 moles of A in a one litre vessel, the number of moles of reactant after 10 minutes will be
(a) 10
(b) 5
(c) 6
(d) 4.

Ans:–(d) 4.

Question 11  On increasing the temperature of the reacting system by 10° the rate of reaction almost becomes double. The most appropriate reason for this is that
(a) Activation energy decreases by increases of temperature

(b) The fraction of molecules having threshold energy increases
(c) Collision frequency increases
(d) The value of threshold energy decreases.

Ans :- (b) The fraction of molecules having threshold energy increases

Question 12 . For the reaction, NO₂ (g) + CO (g) → NO (g), the correct expression for the rate of the reaction is
(a) rate = −𝑑[𝑁𝑂2]/𝑑𝑡
(b) rate = −𝑑[𝐶𝑂2]/𝑑𝑡
(c) rate = 𝑑[𝑁𝑂2]−𝑑[𝐶𝑂]/𝑑𝑡
(d) rate = 𝑑[𝐶𝑂2]/𝑑𝑡

Ans :-(a) rate = −𝑑[𝑁𝑂2]/𝑑𝑡

Question 13:- 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

Ans :-(c) Half

Question 14.:– In the formation of S02 by contact process;

2SO₂ + O₂ → 2SO₃, the rate of reaction was measured as −𝑑[O2]𝑑𝑡 = 2.5 × 10^-4 mol L^-1s^-1. at
The rate of formation of of S03 will be
(a) -5.0 × 10^-4 mol L^-1s^-1
(b) -1.25 × 10^-4 mol L^-1s^-1
(c) 3.75 × 10^-4 mol L^-1s^-1
(d) 5.00 × 10^-4 mol L^-1s^-1

Ans:-(d) 5.00 × 10^-4 mol L^-1s^-1

Question-15. 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

Ans:-(b) 3 × 10^-4 mol L^-1s^-1

Question 16. 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

Ans:- (d) CH₃CHO → CH₄ + CO

Question 17.
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

Ans :-(c) mol^-2 L² s^-1

Question 18. For 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

Ans :- (a) (i) 2, (ii) 1

Question 19. 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) 3
(d) 0

Ans :–(c) 3

Question 20. 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

Ans :–(d) the time of completion of reaction

Question 21.  The chemical reaction, 2O₃ → 3O₂ proceeds as
O₃ ⇌ O₂ + |O| (fast)
|O| + O₃ → 2O₂ (slow)
The rate law expression will be
(a) Rate = k [O] [O₃]
(b) Rate = k [O₃]² [O₂]^-1
(c) Rate = k [O₃]²
(d) Rate = k [O₂] [O]

Ans :-(b) Rate = k [O₃]² [O₂]^-1

Question 22. The unit of rate and rate constant are same for a
(a) zero order reaction
(b) first order reaction
(c) second order reaction
(d) third order reaction

Ans :–(a) zero order reaction

Question 23. The number of molecules of the reactants taking part in a single step of the reaction is indicative of
(a) order of a reaction
(b) molecularity of a reaction
(c) fast step of the mechanism of a reaction
(d) half-life of the reaction

Ans:–(b) molecularity of a reaction

Question 24. The overall rate of a reaction is governed by
(a) the rate of fastest intermediate’ step
(b) the sum total of the rates of all intermediate steps
(c) the average of the rates of all the intermediate steps
(d) the rate of slowest intermediate step

Ans:-(d) the rate of slowest intermediate step

Question 25. The order of reaction is decided by
(a) temperature
(b) mechanism of reaction as well as relative concentration of reactants
(c) molecularity
(d) pressure

Ans :-(b) mechanism of reaction as well as relative concentration of reactants

Question 26. Rate constant in case of first order reaction is
(a) inversely proportional to the concentration units
(b) independent of concentration units
(c) directly proportional to concentration units
(d) inversely proportional to the square of concentration units

Ans :-(b) independent of concentration units

Question 27.
In pseudo unimolecular reactions
(a) both the reactants are present in low concentration
(b) both the reactants are present in same concentration
(c) one of the reactant is present in excess
(d) one of the reactant is non-reactive

Ans :-(c) one of the reactant is present in excess

Question 28 A first order reaction takes 40 min for 30% decomposition. What will be t₁₂?
(a) 77.7 min
(b) 52.5 min
(c) 46.2 min
(d) 22.7 min

Ans :- (a) 77.7 min

Question 29 A first order reaction has a rate constant 1.15 × 10^-3s^-1. How long time will 5 g of this reactant take to reduce to 3 g?
(a) 444 s
(b) 400 s
(c) 528 s
(d) 669 s

Ans :- (a) 444 s

Question 30 Radioactive disintegration is an example of
(a) zero order reaction
(b) first order reaction
(c) second order reaction
(d) third order reaction

Ans :–(b) first order reaction

Question 31 :-A plot of log (a – x) against time t is a straight line. This indicates that the reaction is of
(a) zero order
(b) first order
(c) second order
(d) third order

Ans :- (b) first order

Question 32  Rate of which reaction increases with temperature?
(a) Exothermic reaction
(b) Endothermic reaction
(c) (a) and (b) both
(d) None of the above

Ans:- (c) (a) and (b) both

Question 33  The activation energy in a chemical reaction is defined as
(a) the difference in energies of reactants and products
(b) the sum of energies of reactants and products
(c) the difference in energy of intermediate complex with the average energy of reactants and products
(d) the difference in energy of intermediate complex and the average energy of reactants

Ans:- (d) the difference in energy of intermediate complex and the average energy of reactants

Question 34 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

Ans :– (c) 16 times

Question 35 :-The chemical reaction, 2O₃ → 3O₂ proceeds as
O₃ ⇌ O₂ + |O| (fast)
|O| + O₃ → 2O₂ (slow)
The rate law expression will be
(a) Rate = k [O] [O₃]
(b) Rate = k [O₃]² [O₂]^-1
(c) Rate = k [O₃]²
(d) Rate = k [O₂] [O]

Ans :–(b) Rate = k [O₃]² [O₂]^-1

Question 36:- The activation energy of a reaction is zero. The rate of the reaction
(a) increases with increase of temperature
(b) decreases with decrease of temperature
(c) decreases with increase of temperature
(d) is nearly independent of temperature

Ans :–(d) is nearly independent of temperature

Question.37 In the reaction, 2N₂O₅ → 4NO₂ + O₂ , initial pressure is 500 atm and rate constant k is 3.38 x 10^-5 s-¹ . After 10 min the final pressure of N₂O₅ is
(a) 490 atm
(b) 250 atm
(c) 480 atm
(d) 420 atm

Ans :-(a) 490 atm

–: End of MCQs Chemical Kinetics for ISC Class 12    :–