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Free download in PDF Class 12 Chemistry Chapter 4 Chemical Kinetics Objective Type Questions and Answers for competitive exams. These short objective type questions with answers are very important for Board exams as well as competitive exams like NEET, AIIMS, JIPMER etc. These short solved questions or quizzes are provided by Gkseries./p>
(1)
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: the time of completion of reaction
(2)
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?
(3)
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
(4)
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
(5)
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: CH3CHO → CH4 + CO
(6)
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
(7)
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: bar min-1, bar1/2 min-1
(8)
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
(9)
If the rate of a reaction is expressed by, rate = A [A]² [B], the order of reaction will be
(10)
For a first order reaction A → B the rate constant is x min−1 . If the initial concentration of A is 0.01M , the concentration of A after one hour is given by the expression.
[A]
0.01 e−x
[B]
1 x10-2 (1-e-60x)
[C]
(1x10-2) e-60x
[D]
none of these
(11)
A zero order reaction X →Product , with an initial concentration 0.02M has a half life of 10 min. if one starts with concentration 0.04M, then the half life is
[A]
10 s
[B]
5 min
[C]
20 min
[D]
Cannot be predicted using the given information
(12)
For a first order reaction A → product with initial concentration x mol L−1 , has a half life period of 2.5 hours . For the same reaction with initial concentration (x/2) mol L−1 the half life is
[A]
(2.5 × 2) hours
[B]
(2.5 / 2) hours
[C]
2.5 hours
[D]
Without knowing the rate constant, t1/2 cannot be determined from the given data
Answer: Without knowing the rate constant, t1/2 cannot be determined from the given data
(13)
The decomposition of phosphine (PH3) on tungsten at low pressure is a first order reaction. It is because the
[A]
rate is proportional to the surface coverage
[B]
rate is inversely proportional to the surface coverage
[C]
rate is independent of the surface coverage
[D]
rate of decomposition is slow
Answer: rate is independent of the surface coverage
(14)
For a reaction Rate = k[acetone]3/2 acetone then unit of rate constant and rate of reaction respectively is
[A]
(mol L-1s-1), (mol-1/2 L1/2 s-1)
[B]
(mol-1/2 L1/2s-1), (mol L-1 s-1)
[C]
(mol1/2 L1/2s-1), (mol L-1 s-1)
[D]
(mol Ls-1), (mol1/2 L1/2 s-1)
Answer: (mol-1/2 L1/2s-1), (mol L-1 s-1)
(15)
The addition of a catalyst during a chemical reaction alters which of the following quantities?
[A]
Enthalpy
[B]
Activation energy
[C]
Entropy
[D]
Internal energy
Answer: Activation energy
(16)
Consider the following statements :
(i) increase in concentration of the reactant increases the rate of a zero order reaction.
(ii) rate constant k is equal to collision frequency A if Ea = 0
(iii) rate constant k is equal to collision frequency A if Ea = °
(iv) a plot of ln(k) vs T is a straight line
(v) a plot of ln (k) vs 1/T is a straight line with a positive slope.
Correct statements are
[A]
(ii) only
[B]
(ii) and (iv)
[C]
(ii) and (v)
[D]
(i), (ii) and (v)
(17)
In a reversible reaction, the enthalpy change and the activation energy in the forward direction are respectively −x kJ mol−1 and y kJ mol−1 . Therefore , the energy of activation in the backward direction is
[A]
( y −x ) kJ mol−1
[B]
( x + y )J mol−1
[C]
( x −y ) kJ mol−1
[D]
( x + y ) × 103 J mol−1
Answer: ( x + y ) × 103 J mol−1
(18)
What is the activation energy for a reaction if its rate doubles when the temperature is raised from 200K to 400K? (R = 8.314 JK-1mol-1)
[A]
234.65 kJ mol−1K−1
[B]
434.65 kJ mol−1K−1
[C]
334.65 J mol−1K−1
[D]
434.65 J mol−1K−1
Answer: 434.65 J mol−1K−1
(19)
Assertion: rate of reaction doubles when the concentration of the reactant is doubles if it is a first order reaction.
Reason: rate constant also doubles
[A]
Both assertion and reason are true and reason is the correct explanation of assertion
[B]
Both assertion and reason are true but reason is not the correct explanation of assertion
[C]
Assertion is true but reason is false
[D]
Both assertion and reason are false
Answer: Assertion is true but reason is false
(20)
The rate constant of a reaction is 5.8 × 10−2 s−1 . The order of the reaction is
[A]
First order
[B]
zero order
[C]
Second order
[D]
Third order
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