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Chemical Kinetics 12 MCQs Questions with Answers
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: (b) 3
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: (d) CH3CHO → CH4 + CO
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
Answer: (a) zero order reaction
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: (a) (i)2, (ii) 1
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
Answer: (c) Half
What will be the fraction of molecules having energy equal to or greater than activation energy, Ea?
(a) K
(b) A
(c) Ae-Ea/Rt
(d) e-Ea/Rt
Answer: (d) e-Ea/Rt
For a unimolecular reaction
(a) the order and molecuiarity of the slowest step are equal to one
(b) molecuiarity of the reaction can be zero, one or two
(c) molecuiarity of the reaction can be determined only experimentally
(d) more than one reacting species are involved in one step
Answer: (a) the order and molecuiarity of the slowest step are equal to one
The half life of the first order reaction having rate constant K = 1.7 x 10-5s-1 is
(a) 12.1 h
(b) 9.7 h
(c) 11.3 h
(d) 1.8 h
Answer: (c) 11.3 h
The order of reaction is decided by
(a) temperature
(b) mechanism of reaction as well as relative concentration of reactants
(c) molecularity
(d) pressure
Answer: (b) mechanism of reaction as well as relative concentration of reactants
Half life period of a first order reaction is 10 min. What percentage of the reaction will be completed in 100 min?
(a) 25%
(b) 50%
(c) 99.9%
(d) 75%
Answer: (c) 99.9%
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: (a) 2 × 10-4
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: (c) 16 times
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: (d) the time of completion of reaction
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
Answer: (d) the rate of slowest intermediate step
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
Answer: (a) 77.7 min
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
Answer: (c) one of the reactant is present in excess
Which of the following is affected by catalyst?
(a) ∆H
(b) ∆S
(c) ∆G
(d) Ea
Answer: (d) Ea
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
Answer: (a) 444 s
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
Answer: (d) the difference in energy of intermediate complex and the average energy of reactants
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
Answer: (b) first order
Rate of which reaction increases with temperature?
(a) Exothermic reaction
(b) Endothermic reaction
(c) (a) and (b) both
(d) None of the above
Answer: (c) (a) and (b) both
According to Maxwell Boltzmann distributon of energy, _________ .
(a) the fraction of molecules with most probable kinetic energy decreases at higher temperatures.
(b) the fraction of molecules with most probable kinetic energy increases at higher temperatures.
(c) most probable kinetic energy increases at higher temperatures.
(d) most probable kinetic energy decreases at higher temperatures.
Answer: (d) most probable kinetic energy decreases at higher temperatures.
Which of the following statements about the catalyst is true?
(a) A catalyst accelerates the rate of reaction by bringing down the activation energy.
(b) A catalyst does not participate in reaction mechanism.
(c) A catalyst makes the reaction feasible by making ∆G more negative.
(d) A catalyst makes equilibrium constant more favourable for forward reaction.
Answer: (a) A catalyst accelerates the rate of reaction by bringing down the activation energy.
A first order reaction is 50% completed in 1.26 × 1014 s. How much time would it take for 100% completion?
(a) 1.26 × 1015 s
(b) 2.52 × 1014 s
(c) 2.52 × 1028 s
(d) infinite
Answer: (d) infinite
If cone, of reactant ‘A’ is increased 10 times and rate of reaction becomes 100 times. What is order with respect to ‘A’?
(a) 1
(b) 1
(c) 3
(d) 4
Answer: (b) 1
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