CHEMICAL KINETICS
1 MARK QUESTIONS
1.The decomposition reaction of ammonia gas on platinum surface has a rate constant K=2.5x10-4
mol l-1sec-1. What is the order of reaction?
2.For a reaction, A + B → Product, the rate law is given by: r = [A]1[B]2. What is the order of the reaction?
3.What are the units of rate constant for a 1st order reaction?
4.A substance with initial concentration ‘a’ follows zero order kinetics. In how much time will
reaction goes to completion?
5. The reaction 2A + B  C + D obeys the rate equation, rate = K[A]2[B]. Find out the order when A is
present in large excess.
6.Express the rate of the following reaction in terms of disappearance of hydrogen in the reaction
3H2 + N2 → 2NH3
7. The decomposition reaction of ammonia gas on platinum surface has a rate constant K = 2.5x10-4
mol L-1min-1. What is the order of reaction?
8.What are the units of rate constant for a 2nd order reaction.
9. In a reaction if the concentration of a reactant A is tripled the rate of reaction becomes twenty-seven times.
What is the order of reaction?
10.Identify the reaction order from the following rate constant, k = 2.3 x 10-5 L mol-1 s-1.
2 MARKS QUESTIONS
1.Derive the expression for rate constant for zero order reaction.
2.Define the following terms.
(i) Molecularity
(ii)Rate constant of a reaction.
3.The decomposition of hydrocarbon follows the equation K = (4.5x1011 sec-1) e-28000K/T. Calculate Ea?
4. For a chemical reaction, ln[R] vs. time (S) plot is given below. For the reaction
(i)What is the order of the reaction?
(ii)What is the unit of rate constant K?
(iii)Given the relationship between K & t ½?
(iv) What does the slope of above line indicate?
X
Ln[R]
Y
5.What is meant by pseudo first order reaction? Give an example of pseudo first order reaction
and write the rate equation for the same.
6.A reaction is of second order with respect to a reactant. Now how rate is affected if the concentration
of the reactant is (i) doubled (ii)reduced to half?
7. (i)For a chemical reaction what is the effect of catalyst on the activation energy?
(ii) For a chemical reaction R → P, the variation in the concentration (R) vs. time (t) plot is given as
(logR)
time
(a) Predict the order of the reaction.
(b)What is the slope of the curve.
8. A reactant has a half life of 10 minutes,
(i) Calculate the rate constant for the 1st order reaction.
(ii)What fraction of the reactant will be left after an hour of the reaction has occurred?
9. For a chemical reaction, what is the effect of a catalyst on the following?
(i)Activation energy of the reaction
(ii)Rate constant of the reaction.
10. For a chemical reaction variation in rate with concentration is shown below?
(i)
(ii)
What is the order of the reaction?
What are the units of rate constant K for the reaction?
3 MARKS QUESTIONS
1.The decomposition of A in to products has value of k as 4.5 X 10 3s-1 at 100C and energy of
activation 60 kJ mol-1. At what temperature would k be 1.5 X 104 s-1.
2. For a decomposition reaction the values of rate constant, K at two different temperatures is
given k1=2.15 x 10 L mol –1 s–1 at 650 K and k2= 2.39 x 10 mol–1 s–1 at 700 K. Calculate the value of
activation energy for this reaction. (R=8.314 J K–1 mol–1).
3.(i) The reaction, A + 2B
C obeys the rate equation, rate = k[A]1/2[B]3/2
What is the order of the reaction?
(ii) What are pseudo first order reactions? Give one example of such reaction.
(iii) Calculate the half-life of a first order reaction whose rate constant is 200 s-1.
4. The rate constant for the first order decomposition of H2O2 is given by the following equation:
log k = 14.34 -1.25 × 104 K/T. Calculate Ea for this reaction and at what temperature will its half-period be
256 minutes? (R=8.314 JK-1mol-1, log 4.5 X 10-5 = - 4.3458).
5. The decomposition of A in to product has value of k as 4.5 x 103 s-1 at 10OC and activation energy
is 60 kJ mol-1. Calculate the temperature at which the value of k will be 1.5 x 104 s-1.
6.The thermal decomposition of HCOOH is a first order reaction with rate constant of 2.4 x 10-3 s-1
at a certain temperature. How long it will take for three fourth of initial quantity of HCOOH to decompose?
(log 0.25 = - 0.6021)
7.A first order reaction has a rate constant value of 0.0051 min-1. If we begin with 0.1 M concentration
of the reactant, how much of the reactant will remain after 3.0 h?
8.The half-life for a first order reaction is 5 x 104 s. What percentage of the initial reactant will react
in 2 h?
9.A first order reaction is 20% complete in 5 min. Calculate the time taken for the reaction to be 60%
Complete.
10.The half-life for decay of radioactive C-14 is 5730 years. An archaeological artifact containing wood
Had only 80% of the C-14 found in a living tree. Estimate the age of the sample.
5 MARKS QUESTIONS
1. (a) For the reaction:
C12H22O11 + H2O
Write:
(i) rate of reaction expression
(ii) rate law equation
(iii) moleculatity
(iv) order of reaction
C6H12O6 + C6H12O6
(b) The following data were obtained during the first order thermal decomposition of SO 2Cl2
at constant volume.
SO2Cl2 (g)→SO2(g) + Cl2(g)
Experiment
1
2
Times/s
0
100
Total pressure/atm
0.5
0.6
Calculate the rate of the reaction when total pressure is 0.65 atm.
2.(a) Explain the effect of temperature on reaction rate.
(b) Catalyst has no effect on the equilibrium constant. Why?
(c) A First order reaction is 20% complete in 20 minutes. Calculate the time it will take the
reaction to complete 80%.
3.(a) List the factors on which the rate of a chemical reaction depends.
(b)The half life for decay of radioactive C14 is 5730 years. An archaeological artifact containing wood
has only 80% of the C14 activity as found in living trees. Calculate the age of the artifact.
(c) Express the rate of the following reaction in terms of disappearance of hydrogen in the reaction.
3H2(g) + N2(g) →2NH3(g)
4.(a) Derive the rate equation for first order reaction.
(b) The rate constant for a first order reaction is 60 s-1. How much time will it take to reduce the conc.
of the reactant to 1/10th of its initial value?
(c) The activation energy of a reaction is 75.2 kJ mol-1 in the absence of a catalyst and 50.14 kJ mol-1
with a catalyst. How many times will the rate of reaction grow in the presence of the catalyst if the
reaction proceeds at 250C ? (R=8.314 JK-1 mol-1, antilog 4.40 = 2.5×104)
5. (a) Derive the rate equation for zero order reaction.
(b)The following data were obtained during the first order thermal decomposition of SO2Cl2 at
Constant Volume.
SO2Cl2(g)
SO2(g) + Cl2(g)
Experiment
Time/s
Total pressure/atm
1
0
0.5
2
100
0.6
Calculate the rate of reaction when total pressure is 0.65 atm.
6.(a)Illustrate graphically the effect of catalyst on activation energy.
(b)Catalysts have no effect on equilibrium constant. Why?
(c)The decomposition of A in to product has value of k as 4.5 x 103 s-1 at 10OC and activation energy
is 60 kJ mol-1. Calculate the temperature at which the value of k will be 1.5 x 104 s-1.
7. (a) A reaction is of first order in A and 2nd order in B. Write the differential rate equation.
How the rate is affected if the conc. of both A and B are doubled?
(b)The rate constant of a reaction increases four fold when the temperature changes from 300k to
320k. Calculate activation energy for the reaction. (R=8.314 J.K mol).
8.(a)Rate constant for first order reaction has been found to be 2.54 X 10-3s-1. Calculate its three-fourth
life.
(b)For a chemical reaction variation in the rate with concentration given below.
Rate
Conc.
(i) What is the order of the reaction?
(ii) What are the units of rate constant for the reaction?
(iii) Derive an expression to calculate the time required for completion of the zero-order reaction.