Chemistry MCQs for Class 12 with Answers Chapter 4 Chemical Kinetics

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Chemistry MCQs for Class 12 with Answers Chapter 4 Chemical Kinetics
Chemistry MCQs for Class 12 with Answers Chapter 4 Chemical Kinetics

Free PDF Download of CBSE Chemistry Multiple Choice Questions for Class 12 with Answers Chapter 4 Chemical Kinetics. Chemistry MCQs for Class 12 Chapter Wise with Answers PDF Download was Prepared Based on Latest Exam Pattern. Students can solve NCERT Class 12 Chemistry Chemical Kinetics MCQs Pdf with Answers to know their preparation level.

MCQ Questions for Class 12 Chemistry Chapter 4 Chemical Kinetics with Answers :-

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  1. The role of a catalyst is to change __.
    (i) gibbs energy of reaction.
    (ii) enthalpy of reaction.
    (iii) activation energy of reaction.
    (iv) equilibrium constant.
Answer

Answer: (iii) activation energy of reaction


2. In the presence of a catalyst, the heat evolved or absorbed during the reaction
_________.
(i) increases.
(ii) decreases.
(iii) remains unchanged.
(iv) may increase or decrease.

Answer

Answer: (iii) remains unchanged.


3. Activation energy of a chemical reaction can be determined by _.
(i) determining the rate constant at standard temperature.
(ii) determining the rate constants at two temperatures.
(iii) determining probability of collision.
(iv) using catalyst.

Answer

Answer: (ii) determining the rate constants at two temperatures


4. Consider the Arrhenius equation given below and mark the correct option.
k = A e^–E /RT
(i) Rate constant increases exponentially with increasing activation energy
and decreasing temperature.
(ii) Rate constant decreases exponentially with increasing activation energy
and decreasing temperature.
(iii) Rate constant increases exponentially with decreasing activation energy
and decreasing temperature.
(iv) Rate constant increases exponentially with decreasing activation energy
and increasing temperature.

Answer

Answer: (iv) Rate constant increases exponentially with decreasing activation energy and increasing temperature


5. Which of the following statements is not correct about order of a reaction.
(i) The order of a reaction can be a fractional number.
(ii) Order of a reaction is experimentally determined quantity.
(iii) The order of a reaction is always equal to the sum of the stoichiometric
coefficients of reactants in the balanced chemical equation for a reaction.
(iv) The order of a reaction is the sum of the powers of molar concentration
of the reactants in the rate law expression.

Answer

Answer: (iii) The order of a reaction is always equal to the sum of the stoichiometric coefficients of reactants in the balanced chemical equation for a reaction.


6. Which of the following statements is correct?
(i) The rate of a reaction decreases with passage of time as the concentration
of reactants decreases.
(ii) The rate of a reaction is same at any time during the reaction.
(iii) The rate of a reaction is independent of temperature change.
(iv) The rate of a reaction decreases with increase in concentration of
reactant(s).

Answer

Answer: (i) The rate of a reaction decreases with passage of time as the concentration of reactants decreases.


7. Rate law for the reaction A + 2B → C is found to be
Rate = k [A][B]
Concentration of reactant ‘B’ is doubled, keeping the concentration of ‘A’
constant, the value of rate constant will be______.
(i) the same
(ii) doubled
(iii) quadrupled
(iv) halved

Answer

Answer: (ii) doubled


8. Which of the following statements is incorrect about the collision theory of
chemical reaction?
(i) It considers reacting molecules or atoms to be hard spheres and ignores
their structural features.
(ii) Number of effective collisions determines the rate of reaction.
(iii) Collision of atoms or molecules possessing sufficient threshold energy
results into the product formation.
(iv) Molecules should collide with sufficient threshold energy and proper
orientation for the collision to be effective.

Answer

Answer: (iii) Collision of atoms or molecules possessing sufficient threshold energy results into the product formation.


9. A first order reaction is 50% completed in 1.26 × 1014 s. How much time
would it take for 100% completion?
(i) 1.26 × 1015 s
(ii) 2.52 × 1014 s
(iii) 2.52 × 1028 s
(iv) infinite

Answer

Answer: (iv) infinite


10. Which of the following statement is not correct for the catalyst?
(i) It catalyses the forward and backward reaction to the same extent.
(ii) It alters ∆G of the reaction.
(iii) It is a substance that does not change the equilibrium constant of a
reaction.
(iv) It provides an alternate mechanism by reducing activation energy
between reactants and products.

Answer

Answer: (ii) It alters ∆G of the reaction.


11. The value of rate constant of a pseudo first order reaction __.
(i) depends on the concentration of reactants present in small amount.
(ii) depends on the concentration of reactants present in excess.
(iii) is independent of the concentration of reactants.
(iv) depends only on temperature.

Answer

Answer: (ii) depends on the concentration of reactants present in excess.


12.
The unit of rate and rate constant are same fora
(a) zero order reaction
(b) first order reaction
(c) second order reaction
(d) third order reaction

Answer

Answer: (a) zero order reaction


13.
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) molecuiarity of a reaction
(c) fast step of the mechanism of a reaction
(d) half-life of the reaction

Answer

Answer: (b) molecuiarity of a reaction


14.
Fora 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

Answer: (a) the order and molecuiarity of the slowest step are equal to one


15.
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

Answer: (d) the rate of slowest intermediate step


16.
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

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


17.
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

Answer

Answer: (b) independent of concentration units


18.
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

Answer: (c) 99.9%


19.
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

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


20.
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

Answer: (a) 77.7 min


21.
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

Answer: (a) 444 s


22.
Radioactive disintegration is an example of
(a) zero order reaction
(b) first order reaction
(c) second order reaction
(d) third order reaction

Answer

Answer: (b) first order reaction


23.
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

Answer: (b) first order


24.
Rate of which reaction increases with temperature?
(a) Exothermic reaction
(b) Endothermic reaction
(c) (a) and (b) both
(d) None of the above

Answer

Answer: (c) (a) and (b) both


25.
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

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


26.
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

Answer: (d) CH3CHO → CH4 + CO


27.
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

Answer: (c) mol-2 L² s-1


28.
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

Answer: (a) (i)2, (ii) 1


29.
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

Answer

Answer: (c) 3


30.
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

Answer: (d) the time of completion of reaction


31.
In chemical equation H2 (g) + I2 (g) \(\rightleftharpoons\) 2HI (g) the equilibrium constant Kp depends on
(a) total pressure
(b) catalyst used
(c) amount of H2 and I2
(d) temperature

Answer

Answer: (b) catalyst used


32.
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

Answer: (b) 3


33.
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

Answer: (a) 2 × 10-4


34.
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

Answer: (b) bar min-1, bar1/2 min-1


35.
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

Answer: (c) 16 times


36. The chemical reaction, 2O3 → 3O2 proceeds as
O3 \(\rightleftharpoons\) 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
(d) Rate = k [O2] [O]

Answer

Answer: (b) Rate = k [O3]² [O2]-1


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