Multiple Choice Questions
1.The role of a catalyst is to change ______________. (i) Gibbs energy of reaction. (ii) Enthalpy of
reaction. (iii) Activation energy of reaction. (iv)Equilibrium constant.
2. In the presence of a catalyst, the heat evolved or absorbed during the reaction ___________. (i)
increases. (ii) decreases. (iii) remains unchanged. (iv) may increase or decrease.
3. Activation energy of a chemical reaction can be determined by _________. (i) determining the
rate constant at standard temperature. (ii) determining the rate constants at two temperatures. (iii)
determining probability of collision. (iv) using catalyst.
4. Consider a first order gas phase decomposition reaction given below : A(g) → B(g) + C(g) The
initial pressure of the system before decomposition of A was pi . After lapse of time ‘t’, total
pressure of the system increased by x units and became pt .The rate constant k for the reaction is
given as _________.
5. Which of the following statements is incorrect about the collision theory of chemical reaction?
(i)It considers reacting molecules or atoms to be hard spheres and ignores their structural features.
(ii) Number of effective collisions determines the rate of reaction. (iii)Collision of atoms or molecules
possessing sufficient threshold energy results into the product formation. (iv) Molecules should
collide with sufficient threshold energy and proper orientation for the collision to be effective.
6. A first order reaction is 50% completed in 1.26 × 10-14 s. How much time would it take for 100%
completion? (i) 1.26 × 1015 s (ii) 2.52 × 10-14 s (iii) 2.52 × 10=28 (iv) infinite
7. Which of the following statements are in accordance with the Arrhenius equation? (i)Rate of a
reaction increases with increase in temperature. (ii)Rate of a reaction increases with decrease in
activation energy. (iii)Rate constant decreases exponentially with increase in temperature. (iv) Rate
of reaction decreases with decrease in activation energy.
8. Consider the Arrhenius equation given below and mark the correct option. k = A e-Ea/RT (i)Rate
constant increases exponentially with increasing activation energy and decreasing temperature. (ii)
Rate constant decreases exponentially with increasing activation energy and decreasing
temperature. (iii) Rate constant increases exponentially with decreasing activation energy and
decreasing temperature. (iv) Rate constant increases exponentially with decreasing activation
energy and increasing temperature.
9. The value of rate constant of a pseudo first order reaction ____________. (i) depends on the
concentration of reactants present in small amount. (ii) depends on the concentration of reactants
present in excess. (iii) is independent of the concentration of reactants. (iv) depends only on
temperature.
10. Which of the following statements are applicable to a balanced chemical equation of an
elementary reaction? (i) Order is same as molecularity. (ii) Order is less than the molecularity. (iii)
Order is greater than the molecularity. (iv) Molecularity can never be zero.
