Important Questions of Chemical Kinetics

Very Short Answer Type Questions  –

  1. What is the unit of the rate constant of second-order reaction?
  2. For which type of reaction, order and Molecularity have the same value?
  3. Define the rate constant.
  4. Give one example of pseudo first order reaction.
  5. How the Molecularity of reaction is different from order of reaction by taking example?
  6. The rate of reaction gets doubled, when the temperature is raised from 298K to 308K. Calculate its activation energy.
  7. The half – life period of the two samples are 0.2 and 05 seconds. Their initial concentrations are 300 and 100 mol/l. What is the order of reaction?
  8. What is half-life period of a reaction?
  9. Why rate of reaction does not remain constant throughout?
  10. Write the rate equation for the reaction 2A + B —> C if the order of the reaction is zero.
  11. Why can’t Molecularity of any reaction be equal to zero?
  12. A first order reaction takes 15 minutes for 25% decomposition. Calculate t1/2 for the reaction.

(log 2 = 0.301, log 3 = 0.4771, log 4 = 0.6021)

13. If the decomposition of nitrogen oxide as –

             2N2O5       —>   4NO2 + O2

follows a first order kinetics.

14. Calculate the rate constant for a 0.05M solution if the instantaneous rate is 1.5 x 10-8 mol/l/s?

15. Is zero order reaction has Molecularity equal to zero?

16. What is the order of photochemical reactions?Identify the reaction order from the rate constant value = 3.2 x 10-5 litre/mol/sec.

Short Answer type Questions –

  1. What is the difference between order and Molecularity of reaction?
  2. Write the Arrhenius equation which relates the rate constant with temperature.
  3. The rate constant of a first order reaction increases from 2 x 10-2 to 4 x 10-2 when the temperature changes from 300 K to 310 K. Calculate the energy of activation (Ea).

(log 2 = 0.301, log 3 = 0.4771, log 4 = 0.6021)

4. Explain the factors affecting the rate of reaction.

5. What do you understand by rate law and rate constant of a reaction?

6. What is half – life period? Derive and expression for the half – life period for the first order reaction.

7. Explain the effect of temperature on the rate constant of a reaction.

8. A reaction is second order with respect to reactant. How is its rate affected if the concentration of the reactant is (i) doubled (ii) reduced to half.

9.Why the rate of a reaction does increases with rise in temperature?

10. The activation energy for a reaction at the temperature T K was found to be 2.303 RT J/mol. Calculate ratio of the rate constant to Arrhenius factor.

11. For the reaction, N2O5 (g)  —> 2NO2 (g) + ½ O2 (g) the value of rate of disappearance of N2O5 is given as 6.25 x 10-3 mol L-1 s-1. Calculate rate of formation of NO2 and O2.

12.Define threshold energy and activation energy. How they are related?

13. How the rapid change in the concentration of reactant and product monitored for fast reactions?

14.Why the slow reactions require the less activation energy?

15. Explain why the reaction rate does not remain constant throughout the reaction.

Long Answer Type Questions –

  1. For a reaction, A + B  —> P, rate is given by –

                     Rate = [A]2[B]

What is the overall order of a reaction, if B is present in excess?

2. If the concentration of A is doubled, the how is the rate of reaction effected?

3. If a first-order reaction takes 23.1 minutes for 50% completion. Calculate the time required for 75 % completion of this reaction.

(log 2 = 0.301, log 3 = 0.4771, log 4 = 0.6021)

4. What do you mean by order of reaction? Derive the equation for the rate constant for the first order reaction. Also, write the units of rate constant if the concentration is expressed in moles per liter and time in seconds.

5. Explain the difference between the instantaneous rate of a reaction and average rate of a reaction.

6. Derive the integrated rate law equation for the first order reaction. Derive the relation between t1/2 and k from the expression.

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