MCQ Questions Chapter 4 Chemical Kinetics Class 12 Chemistry

MCQ Class 12

Please refer to MCQ Questions Chapter 4 Chemical Kinetics Class 12 Chemistry with answers provided below. These multiple-choice questions have been developed based on the latest NCERT book for class 12 Chemistry issued for the current academic year. We have provided MCQ Questions for Class 12 Chemistry for all chapters on our website. Students should learn the objective based questions for Chapter 4 Chemical Kinetics in Class 12 Chemistry provided below to get more marks in exams.

Chapter 4 Chemical Kinetics MCQ Questions

Please refer to the following Chapter 4 Chemical Kinetics MCQ Questions Class 12 Chemistry with solutions for all important topics in the chapter.

MCQ Questions Answers for Chapter 4 Chemical Kinetics Class 12 Chemistry

Question. Half-life of a hypothetical reaction is found to be inversely proportional to the cube of initial concentration. The order of reaction is
(a) 4
(b) 3
(c) 5
(d) 2                   

Answer

A

Question. The half-life of a second order reaction, A → B is given as
(a) t1/2 = 0.693/k
(b) t1/2  = k[A]0
(c) t1/2 = [A]0/
(d) t1/2 = 1/k[A]0                   

Answer

D

Question.  A drop of a solution (volume = 0.05 mL) contains 6 ×10–7 mole of H+ .If the rate of disappearance of H+ is 6.0 10× 5 mol L–1 s–1, how long will it take for the H+ in the
drop to disappear?
(a) 8.0 × 10–8s
(b) 2.0 × 10–8s
(c) 6.0 × 10–6s
(d) 2.0 × 10–2s       

Answer

B

Question. For the reaction system,
      2NO( ) + O2( g ) → 2NO2( g ) 
volume is suddenly reduced to half its value by increasing the pressure on it. If the reaction is of first order with respect to O2 and second order with respect to NO; the rate of reaction will
(a) diminish to one fourth of its initial value
(b) diminish to one eighth of its initial value
(c) increase to eight times of its initial value
(d) increase to four times of its initial value             

Answer

C

Question. The instantaneous rate of disappearance of MnO4 ion in the following reaction is 4.56 ×10−3 Ms−1
2MnO4 + 10I + 16H+ → 2Mn2+ + 5I2 + 8H2O

The rate of appearance I2  is
(a) 4.56 × 10−4 M s−1
(b) 1.14 × 10−2 M s−1
(c) 1.14 × 10−3 M s−1
(d) 5.7 × 10−3 M s−1         

Answer

B

Question. Consider a reaction, aG + bH → products,when concentration of both the reactants G and H is doubled, the rate increases by eight times. However, when concentration of G is doubled keeping the concentration of H fixed, the rate is doubled. The overall order of the reaction is            
(a) 0
(b) 1
(c) 2
(d) 3                 

Answer

D

Question. The rate for the decomposition of NH3 on platinum surface is zero order. What are the rate of production of N2 and H2 respectively, if k = 2.5 ×10−4 mol L−1s−1?
(a) 1.25 × 10−4 mol L−1 s−1 ; 3.75 × 10−4 mol L−1s−1
(b) 3.75 × 10−4 mol L−1 s−1 ; 1.25 × 10−4 mol L−1s−1
(c) 2.5 × 10−4 mol L−1 s−1 ; 3.75 × 10−4 mol L−1s−1
(d) 1.25 × 10−4 mol L−1 s−1 ; 2.5 × 10−4 mol L−1s−1        

Answer

A

Question. The rate constant of a zero order reaction is 2.0 × 10−2 mol L−1 s−1. If the concentration of the reactant after 25 s is 0.5 M, what is the initial concentration?
(a) 0.5 M
(b) 1.25 M
(c) 12.5 M
(d) 1.0 M                     

Answer

D

Question. At 518°C, the rate of decomposition of a sample of gases acetaldehyde, initially at a pressure of 363 torr, was 1.00 torr s−1 when 5% had reacted and 0.5 torr s−1, when 33% had reacted. The order of the reaction is
(a) 2
(b) 3
(c) 1
(d) 0                

Answer

A

Question. The rate constant for a zero order reaction is
(a) k = C0 /2t
(b) k = C0–Ct / t 
(c) k =ln C0–Ct/t 
(d) k = C0/Ct           

Answer

B

Question. The time for half-life period of a certain reaction, A → products is 1 h. When the initial concentration of the reactant ‘ A’ , is 2.0 mol L−1, how much time does it take for its concentration to come from 0.50 to 0.25 mol L−1, if it is a zero order reaction? 
(a) 4 h
(b) 0.5 h
(c) 0.25 h
(d) 1 h           

Answer

C

Question. For a first order reaction, A → Products, the concentration of A changes from 0.1 M to 0.025 M in 40 min. The rate of reaction when the concentration of A is 0.01 M is 
(a) 1.73 ×10−5 M/min  
(b) 3.47 × 10−4 M/min
(c) 3.47 × 10−5 M/min 
(d) 1.73 × 10−4 M/min           

Answer

B

Question. The rate of a chemical reaction doubles for every10°C rise of temperature. If the temperature is raised by 50°C, the rate of the reaction increases by about
(a) 10 times
(b) 24 times
(c) 32 times
(d) 64 times                     

Answer

C

Question. The half-life period of a first order chemical reaction is 6.93 min. The time required for the completion of 99% of the chemical reaction will be (log 2 = 0.301)
(a) 230.3 min
(b) 23.03 min
(c) 46.06 min
(d) 460.6 min               

Answer

C

Question. An organic compound undergoes first orderdecomposition. The time taken for its decomposition to 1/8 and 1/10 of its initial concentration are t1/8 and t1/10 respectively.
What is the value of [t1/8/t1/10] ×10? (log102 = 0.3) 
(a) 2
(b) 3
(c) 6 
(d) 9           

Answer

D

Question. Select the correct statement.
(a) A collision between reactant molecules must occur with a certain minimum energy before it is effective in yielding product molecule
(b) d(logk)/dt = Ea/2.303RT2 is called Arrhenius equation
(c) Both (a) and (b)
(d) None of the above                       

Answer

C

Question. H2O  and O-atom react in upper atmosphere bimolecularly to form twoOH radicals. ΔH for the reaction is 72 kJ mol−1 at 500 K and energy of activation is 77 kJ mol−1. Ea for bimolecular recombination of two OH radicals to form H2O  and O-atom will be
(a) 5 kJ mol−1
(b) 72 kJ mol−1
(c) 77 kJ mol−1
(d) 149 kJ mol−1                 

Answer

A

Question. For a first order reaction, the time required for 99.9% of the reaction to take place is nearly
(a) 10 times that required for half of the reaction
(b) 100 times that required for half of the reaction
(c) 10 times that required for one fourth of the reaction
(d) 20 times that required for half of the reaction                 

Answer

B

Question. A first order reaction is half-completed in 45 min. How long does it need for 99.9% of the reaction to be completed?
(a) 20 h
(b) 10 h
(c) 71/2 h
(d) 5 h             

Answer

C

Question. The rate of reaction is doubled for every 10°C rise in temperature. The increase in the reaction rate as a result of temperature rise from 10°C to 100°C is
(a) equal to the energy of activation of products
(b) 112 times
(c) 512 times
(d) 614 times             

Answer

C

Question. Under the same reaction conditions, initial concentration of 1.386mol dm–3 of a substance becomes half in 40 s and 20 s through first order and zero order kinetics respectively. Ratio (k1 / k0 ) of the rate constants for first order (k1) and zero order (k0) of the reaction is
(a) 0.5 mol–1 dm3
(b) 1.0 mol–1 dm–3
(c) 1.5 mol–1 dm–3
(d) 2.0 mol–1 dm3             

Answer

A

Question. Higher order (> 3) reactions are rare due to
(a) low probability of simultaneous collision of all the reacting species
(b) increase in entropy and activation energy as more molecules are involved
(c) shifting of equilibrium towards reactants due to elastic coillisions
(d) loss of active species on collision               

Answer

A

Question. The following mechanism has been proposed for the reaction of NO with Br2 to form NOBr
           NO(g) + Br2(g) → NOBr2(g)
      NOBr2(g) + NO(g) → 2NOBr(g)
If the second step is the rate determining step, the order of the reaction with respect to NO(g) is
(a) 1
(b) 0
(c) 3
(d) 2               

Answer

D

Question. The hydrolysis of methyl formate in acid solution has rate expression : rate =k [HCOOCH3 ][H+ ]
  The balanced equation being
     HCOOCH3 + H2O → HCOOH + CH3OH 
The rate law contains [H+ ] , though the balanced equation does not contain [H+ ]because
(a) H+ ion is a catalyst
(b) H+ is an important constituent of any reaction
(c) more for convenience to express the rate law
(d) all acids contain H+ ions                 

Answer

A

Question. The role of a catalyst is to change …….
(a) Gibbs energy of reaction
(b) enthalpy of reaction
(c) activation energy of reaction
(d) equilibrium constant             

Answer

C

Question. Rate constant k varies with temperature as given by equation
          logk (min−1 ) = 5− 2000 K / T
Consider the following about this equation
I. Pre-exponential factor is10 5
II. Ea is 9.212 kcal
III. Variation of log k with 1/T is linear
Select the correct statement.
(a) I, II, III
(b) I, III
(c) II, III
(d) I, II                     

Answer

A

Question. The hydrolysis of sucrose into glucose and fructose,
           C12H22O11 + H2O → C6H12O6 + C6H12O6 
follows first order kinetics. In a neutral solution, if at 27°C, rate constant is 2.1 × 10−11 s−1 and at 37°C, rate constant is 8.5 × 10−11 s−1. The rate constant at 47°C will be
(a) 4.04
(b) 3.163 × 10−10
(c) 8.5 × 10−11
(d) 1.785 × 10−21                       

Answer

B

Question. Decomposition of H2O2 follows a first order reaction. In 50 min, the concentration of H2O2 decreases for 0.5 to 0.125 M in one such decomposition. When the concentration of H2O2 reaches 0.05 M, the rate of formation of O2 will be 
(a) 6.93 × 10−4 . ×  mol min−1
(b) 2.66 L min−1 at STP
(c) 134 ×10−2 mol min−1
(d) 6.93 × 10−2 mol min−1               

Answer

A

Question. The plot of log k versus 1/T is linear with a slope of
(a) −E/ R
(b) EΙR a
(c) −Ea /2.303 R
(d) Ea/2.303 R                                         

Answer

C

Question. The rate of a reaction doubles when its temperature changes from 300 K to 310 K. Activation energy of such a reaction will be
       [R = 8.314 JK−1 mol−1 log2 = 0.301]
(a) 48.6 kJ mol−1
(b) 58.5 kJ mol−1
(c) 60.5 kJ mol−1
(d) 53.6 kJ mol−1                         

Answer

D

Question. Consider the reaction,
Cl2( aq ) + H2S (aq) → S(s) + 2H+ (aq) + 2Cl(aq)
The rate equation for this reaction is,
         rate [Cl2 [H2S] = k ]
Which of these mechanisms is/are consistent with this rate equation?
I. Cl2 + H2S → H+ + Cl + Cl+ + HS–                 (slow) 
   Cl+ + HS →  H+ + Cl + S                        (fast)

II. H2S ⇌ H+ + HS                           (fast equilibrium)
    Cl2 + HS → 2Cl + H+ + S               (slow)
(a) Only II
(b) Both I and II
(c) Neither I nor II
(d) Only I                       

Answer

D

Question.  For an endothermic reaction, where ΔH represents the enthalpy of the reaction in kJ/mol, the minimum value for the energy of activation will be
(a) less than ΔH
(b) zero
(c) more than ΔH
(d) equal to ΔH           

Answer

C

Question.  The reaction, X → Y is an exothermic reaction. Activation energy of the reaction for conversion of X into Y is 150 kJ mol−1. Enthalpy is 135 kJ mol−1. The activation energy for the reverse reaction,Y → X will be
(a) 280 kJ mol−1
(b) 285 kJ mol−1
(c) 270 kJ mol−1
(d) 15 kJ mol−1           

Answer

B

Question.  The gas phase decomposition of dimethyl ether follows first order kinetics
        CH3OCH3(g) → CH4(g) + H2(g)+CO(g)
The reaction is carried out in constant volume container at 500°C and has a half-life of 14.5 min. Initially, only dimethyl ether is present at a pressure of 0.4 atmosphere. What is the total pressure of the system after 12 min ?
(a) 0.564 atm
(b) 0.1744 atm
(c) 0.693 atm             
(d) 0.249 atm

Answer

B

Question. The half-life period for first order reaction having activation energy 39.3 kcal mol−1 at 300°C and frequency constant 1.11 × 1011s−1  will be
(a) 1 h
(b) 1.68 h
(c) 1.28 h
(d) 1.11h             

Answer

B

Question. During nuclear explosion, one of the product is 90Sr with half-life of 28.1 yr. If1μg of 90Sr was absorbed in the bones of a newly born baby instead of calcium, how much of it will remain after 10 yrs and 60 yrs if it is not lost metabolically ?
(Nuclear explosions follow first order kinetics).
(a) 0.7814 μg and 0.227 μg
(b) 0.227 μg and 0.7814 μg
(c) 0.9338 μg and 0.3323 μg
(d) 0.500 μg and 0.300 μg                 

Answer

A

Question.  Consider the Arrhenius equation given below and mark the correct option.
               k = Ae−Ea/RT
(a) Rate constant increases exponentially with increasing activation energy and decreasing temperature
(b) Rate constant decreases exponentially with increasing activation energy
(c) Rate constant increases exponentially with decreasing activation energy and decreasing temperature
(d) Rate constant increases exponentially with decreasing activation energy and increasing temperature                       

Answer

D

Question.  The half-life for the reaction, N2O5 → 2NO2 + 1/2 O2 is 24 h at 30°C. Starting with 10 g of N2O5, how many grams of N2O5 will remain after a period of 96 h ?
(a) 1.25 g
(b) 0.63 g
(c) 1.77 g
(d) 0.5 g                 

Answer

B

Question.  Calculate the half-life of the first order reaction,
      C2H4O(g) ⇔ CH4 (g) + CO(g)
if the initial pressure of C2H4O (g) is 80 mm and the total pressure at the end of 20 min is 120 mm.
(a) 40 min
(b) 120 min
(c) 20 min
(d) 80 min                       

Answer

C

Question. The energies of activation for forward and backward reactions for A2 + B2 ⇔ 2AB are 180 kJ mol–1 and 200 kJ mol–1 respectively. The presence of a catalyst lowers the activation energy of both (forward and backward) reactions by 100 kJmol–1. The enthalpy change of the reaction (A2 + B2 → 2AB) in the presence of catalyst will be (in kJ mol–1)
(a) 300
(b) −120
(c) 280
(d) − 20                                 

Answer

D

Question. Which one of the following statements is incorrect about the molecularity of a reaction?
(a) Molecularity of a reaction is the number of molecules of the reactants present in the balanced equation
(b) Molecularity of a reaction is the number of molecules in the slowest step
(c) Molecularity is always a whole number
(d) There is no difference between order and molecularity of a reaction     

Answer

D

Question. The reaction, 2N2O5 ⇌ 2N2O4 + O2 is
(a) bimolecular and second order
(b) unimolecular and first order
(c) bimolecular and first order
(d) bimolecular and zero order       

Answer

C

Question. The reaction 2A + B + C → D + E is found to be first order in A, second in B and zero order in C. What is the effect on the rate of increasing concentration of A, B and C two times ?
(a) 72 times
(b) 8 times
(c) 24 times
(d) 36 times
(e) None of these      

Answer

B

Question. Rate of a reaction can be expressed by the following rate expression, Rate = k[ A]2[B], if concentration of A is increased by 3 times and concentration of B is increased by 2 times, how many times rate of reaction increases? 
(a) 9 times
(b) 27 times
(c) 18 times
(d) 8 times     

Answer

C

Question. Inversion of cane-sugar in dilute acid is a
(a) bimolecular reaction
(b) pseudo-unimolecular reaction
(c) unimolecular reaction
(d) trimolecular reaction   

Answer

B

Question. For the first order reaction half-life is 14 s, the time required for the initial concentration to reduce to l /8 of its value is
(a) (14 )3 s
(b) 28 s
(c) 42 s
(d) (14 )2 s     

Answer

C

Question. Which one is not correct ?
(a) Rate of zero order reaction depends upon initial concentration of reactant
(b) Rate of zero order reaction does not depend upon initial concentration of reactant
(c) t1/2 of first order reaction is independent of initial concentration of reactant
(d) t1/2 of zero order reaction is dependent of initial concentration of reactant   

Answer

A

Question. Which expression is wrong for first order reaction?
(a) k = 2.303/t log (A0 / At )
(b) k = t/2.303 log (A0 / At )
(c) -k = t/2.303 log (At / A0 )
(d) Rate = k[A]   

Answer

B

Question. The rate equation for the reaction 2A + B ➔ C is found to be rate = k [A ] [ B] The correct statement in relation to this reaction is that the 
(a) unit of k must be s-1
(b) t1/2 is a constant
(c) rate of fo1mation of C is twice the rate of disappearance of A
(d) value of k is independent of the initial concentrations of A andB   

Answer

C

Question. A reaction was found to be second order with respect to the concentration of carbon monoxide. If the concentration of carbon monoxide is doubled, with everything else kept the same, the rate of reaction will 
(a) remain unchanged
(b) triple
(c) increases by a factor of four
(d) double     

Answer

C

Question. The following mechanism has been proposed for the reaction of NO with Br2 to fonn NOBr
NO(g) + Br2 (g) ⇌ NOBr2 (g)
NOBr2 (g) + NO (g) → 2NOBr(g)
If the second step is the rate determining step, the order of the reaction with respect to NO (g) is 
(a) 1
(b) 0
(c) 3
(d) 2   

Answer

D

Question. For which order half-life period is independent of initial concentration ? 
(a) Zero
(b) First
(c) Second
(d) Third       

Answer

B

Question. Which of the following is not the example of pseudo unimolecular reactions? 
(a) CH3COOC2H5 + H2O →H+ CH3COOH + C2H5OH
(b) C12H22O11 + H2O →H+ C6H12O6 + C6H12O6
                                        Glucose        Fructose
(c) CH3COCI + H2O → CH3COOH + HCl
(d) CH3COOC2H5 + H2O →H- CH3COOH + C2H5OH     

Answer

D

Question. The following homogeneous gaseous reactions were experimentally found to be second order overall.
I. 2NO → N2 + O2
II. 3O2 → 2O3
III. N2O3 → NO + NO2
IV. H2 + I2 → 2HI
Which of these are most likely to be elementary reactions that occur in one step ? 
(a) Only III
(b) I and III
(c) I and IV
(d) III and IV
(e) I, II and III       

Answer

C

Question. For a first order reaction with rate constant ‘k’ and initial concentration ‘a’, the half-life period is given by 
(a) ln 2/k
(b) 1/ka
(c) 3/2k-a2
(d) None of these       

Answer

A

Question. The rate constant for a first order reaction whose half-life, is 480 s is 
(a) 2.88 x 10-3 s-1
(b) 2.72 x 10-3 s-1
(c) 1.44 x 10-3 s-1
(d) 1.44s-1     

Answer

C

Question. For the following homogeneous reaction, the unit of rate constant is A + B →k C
(a) mol-1 Ls-1
(b) s-1
(c) s
(d) s-1 mol L-1   

Answer

A

Question. For a reaction A + B → C + D, if the concentration of A is doubled without altering the concentration of B, the rate gets doubled. If the concentration of B is increased by nine times without altering the concentration of A, the rate gets tripled. The order of the reaction is 
(a) 2
(b) 1
(c) 3/2
(d) 4/3     

Answer

C

Question. Find the two-third life (t2/3 ) of a first order reaction in which k = 5.48 x 10-14 per second
(a) 201 X 1013
(b) 2.01 X 1013
(c) 201 X 1020
(d) 0.201 X 1010
(e) None of these    

Answer

B

Question. In a chemical reaction, two reactants take part. The rate of reaction is directly proportional to the concentration of one of them and inversely proportional to the concentration of the other. The order of reaction is 
(a) 0
(b) 1
(c) 2
(d) 4     

Answer

A

Question. A hydrogenation reaction is carried out at 500 K. If the same reaction is carried out in the presence of a catalyst at the same rate, the temperature required is 400 K. What will be the activation energy of the reaction if the catalyst lowers the activation energy barrier by 20 kJ mol−1 ?
(a) 120 kJ mol−1
(b) 80 kJ mol−1
(c) 100 kJ mol−1
(d) 20 kJ mol−1                   

Answer

C

Question. Two reactions R1 and R2 have identical pre-exponential factors. Activation energy of R1 exceeds that of R2 by 20 kJ mol−1. If k1 and k2 are rate constant for reactions R1 and R2 respectively at 300 K, then ln{k2/k1} is equal to [R = 8.314J mol−1 K−1 ]  
(a) 8
(b) 12
(c) 6
(d) 4                       

Answer

D

Question. The chemical reaction, 2O3 → 3O2, proceeds as follows:
       O3 ⇌ O2 + O                           (fast)
      O + O3 → 2O2                         (slow)
The rate law expression should be
(a) r = k′[O3 ]2
(b) r = k′[O3 ]2 [O2 ]−1
(c) r =k′[O3 ] [O2 ]
(d) Unpredictable                     

Answer

B

Question. The rate law for the reaction,
R Cl + NaOH(aq) → R OH + NaCl is given by, rate = k [R Cl]. The rate of the reaction will be
(a) doubled on doubling the concentration of sodium hydroxide
(b) halved on reducing the concentration of alkyl halide to one half
(c) decreased on increasing the temperature of the reaction
(d) unaffected by increasing the temperature of the reaction                 

Answer

B

Question. The units of second order rate constant is
(a) mol dm–3 s–1
(b) s–1
(c) dm3 mol–1 s–1
(d) None of these           

Answer

C

MCQ Questions Chapter 4 Chemical Kinetics Class 12 Chemistry

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