1. Substance A disappears following zero order kinetics with rate constant as 0.015 M s-1. Estimate the concentration of A left after 25 seconds if the initial concentration is 0.5 M ?
a) 0.125 M
b) 0.375 M
c) 0.48 M
d) 0.25 M
2. A first order reaction has half-life 10 min. If the reaction is started with 80 mol L-1, calculate the rate after 30 min.
a) 0.0693
b) 0.693
c) 0.4606
d) 0.04606
3. Half-life of a reaction is 1/3 of the time required for the 75% completion of reaction. What is the order of reaction ?
a) 3
b) 1
c) 0
d) 2
4. A straight line graph for a second order will be obtained when the graph is plotted:
(A) time vs (conc) -1
(B) (conc) -1 vs time
(C) Log(conc) vs time
(D) Conc vs time
5. The rate constant for a certain reaction can be expressed as:
log10 k = 4 -
Then the pre-exponential factor is:
(a) 10 4
(b)10 8
(c)2 X 10 4
(d) 2 X 10 8
6. On increasing the temperature of the reaction, the rate of reaction also increases . This is due to:
(a) Increase in collision frequency
(b) Decrease in average kinetic energies of colliding molecules.
(c) Decrease in activation energy of the reaction.
(d) Increase in fraction of molecules with energies which exceeds the activation energy.
7. For a complex reaction, 2A + B ------> C, the molecularity of the reaction is:
(A) 2
(B) 1
(C) 3
(D) not defined.
8. For the decomposition of A2S into A2 and X follows second order kinetics:
k = (5.0 X 10 11) e-2000/T
Calculate the energy of activation?
(A) 4000 cal
(B) 16628 cal
(C) 4 kcal
(D) 8.314 Kcal
2000 X 2 = 4000 cal = 4 kcal.
9. For a exothermic forward reaction, if the enthalpy of the reaction is 20 KJ/mol and the energy of activation is 50 KJ/mol. The activation energy for the backward reaction will be:
(A) 50 KJ mol-1
(B) 70 KJ mol-1
(C) 30 KJ mol-1
(D) 20 KJ mol-1
10. Select the correct statement(s) for second order kinetics
(I) lesser the initial concentration, higher will be the half-life.
(II) The unit of rate constant is mol -1 L s -1
(III) half-life is independent upon the initial concentration.
(A) I
(B) II
(C) III
(D) I, III
2. The function of the catalyst is to:
(A) increase the rate of reaction
(B) decrease the kinetic energies
(C) decreasse the activation energy
(D) increase the collision factor.
3. The time required for the 99% completion of the first order reaction is:
(A) twice the time required for the 90 % completion
(B) dependent upon initial concentration
(C) doubled with doubling the initial concentration
(D) independent of initial concentration
4. A pseudo order is a reaction which has:
(A) excess of a reactant
(B) high order
(C) not exactly first order kinetics.
(D) zero order kinetics sometimes.
5. Number of collisions per unit time are dependent upon :
(A) number of molecules in the colliding molecules.
(B) Size of the molecules
(C) average speed of the molecules
(D) shape of the molecules
Integer type
1. If the rate of a first order reaction is 0.04 mol L -1 s-1 at 10 min and 0.03 mol L -1 s-1 at 20 min after the starting point, What will be the half-life of the reaction ?
2. A substance radioactive in nature decomposes 20 % in 10 min. After what time ( in minutes) will the number of atoms be reduced to 1018 atoms if initially, there were 5 X 1020 atoms present ?
3. The activation energy of the reaction is 75.2 KJ/mol in the absence of catalyst and 50.14 KJ/mol in the presence of the catalyst. How many times the rate of reaction grow in presence of catalyst at 298 K?
4. The decomposition of SO2Cl2 into sulphur dioxide and chlorine gas follows first order kinetics with half-life 3.15 X 104 sec. what percentage of the reactant will decompose on heating at 575 K for 90 minutes ?
5. A first order reaction is 20% completed in 10 mins. calculate the time required for 75% completion of the reaction.