This set of Physical Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Kinetics Definition and Types”.
1. In a reaction, A + B → Product, when the concentration of B is doubled the rate is doubled, and when the concentrations of both the reactant doubled the rate is increased by a factor of 8, rate law can be written as:
a) Rate = k[A]2[B]
b) Rate = k[A][B]2
c) Rate = k[A][B]
d) Rate = k[A]2[B]2
View Answer
Explanation: Rate law can be written as Rate = k[A]2[B]2. Doubling the concentration of a reactant will cause the rate to double.
2. In zero order reaction when the temperature rises by 10℃, the rate is doubled. What will be the rate of reaction if the temperature is increased by 10℃ to 100℃?
a) 128 times
b) 256 times
c) 64 times
d) 512 times
View Answer
Explanation: The rate is doubled when the temperature rises by 10℃. For temperature 10 to 100℃, the number of rises is 9. ((100-10)/10) = 9. So, 2n = 29 = 512.
3. In the first-order reaction which of the following changes with time?
a) Full life
b) Half-life
c) Rate constant
d) Rate of reaction
View Answer
Explanation: The rate of reaction changes with time. It decreases with time because the reaction goes quickly when there are lots of reactants, but slows down when there are fewer reactants.
4. What is the time required for 100% completion of zero order reaction?
a) a/2k
b) 2k/a
c) ak
d) a/k
View Answer
Explanation: The time required is a/k. It has a rate that is independent of the concentration of the reactants.
5. What is the half-life for zero order reaction?
a) [A]0/2k
b) A02k
c) [2A]0/k
d) A0/k
View Answer
Explanation: It describes the time needed for half of the reactant to be depleted. The half-life for a zero order is [A]0/2k.
6. Arrhenius factor shows the effect of change of temperature.
a) True
b) False
View Answer
Explanation: It shows the effect of change of temperature on the rate constant and on the rate of reaction. The frequency factor is nearly constant.
7. Radioactivity decreases 90% of a sample after 10 years. Calculate the half-life of the sample?
a) 2 years
b) 5 years
c) 10 years
d) 3 years
View Answer
Explanation: The half-life would be 3 years. A radioactive life means the amount of time it takes for the isotope to decay.
8. Activation energy is the minimum energy to start a reaction.
a) False
b) True
View Answer
Explanation: It is the energy which must be available to the potential reactants to result in a chemical reaction. It can also be defined as the minimum energy to start a reaction.
9. What is the first order rate law?
a) ln[A] = -kt + ln[A]0
b) ln[A] = -kt
c) [A]t = -kt + [A]0
d) r = k
View Answer
Explanation: The integrated first law is: ln[A] = -kt + ln[A]0. A graph of ln[A] vs time t gives a straight line with a slope of -k.
10. What is the half-life for the first-order reaction?
a) [A]0/2k
b) [2A]0/k
c) ln (2)/k
d) r = k[A]
View Answer
Explanation: The half-life of the first order reaction is independent of the concentration. The half-life of the first order is given as ln (2)/k.
Sanfoundry Global Education & Learning Series – Physical Chemistry.
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