The rate expression for a heterogeneous catalytic reaction is given by, – rA = K.KA PA(1 + KA.PA + KR.PR), where K is surface reaction rate constant and KA and KR are absorption equilibrium constants of A and R respectively. If KR PR >> (1 + KA PA), the apparent activation energy EA is equal to (given E is the activation energy for the reaction and ΔHR and ΔHA are the activation energies of adsorption of R and A) ?

Related Mcqs:

1. The rate controlling step for the heterogeneous irreversible catalytic reaction A(g) + B(g) → C(g) is the surface reaction of absorbed A with absorbed B to give adsorbed C. The rate expression for this reaction can then be written as (where, KA, KB and KC are the equilibrium constants and is the rate constant of the rate controlling step) ?

   A. k KA pApB / (1 + KApA + KBpB)
   B. k KAKB pApB / (1 + KApA + KBpB)
   C. k KAKB pApB / (1 + KApA + KBpB + KCpC)
   D. k KAKB pApB / (1 + KApA + KBpB + KCpC)2

2. The rate of the heterogeneous catalytic reaction A(g) + B(g) → C(g) is given by -rA = k.KA.pA.PB/(1 + KA.PA + Kc.pc), where KA and Kc are the adsorption equilibrium constants. The rate controlling step for this reaction is_______________?

   A. Absorption of A
   B. Surface reaction between absorbed A and absorbed B
   C. Surface reaction between absorbed A and B in the gas phase
   D. Surface reaction between A in the gas phase and absorbed B

3. If the pore diffusion controls in a catalytic reaction, the apparent activation energy Ea is equal to___________________?

   A. The intrinsic activation energy E
   B. (E + ED) where ED is activation due to diffusion
   C. (E + ED)/2
   D. ED/2

4. At a given value of E/R (ratio of activation energy and gas constant), the ratio of the rate constants at 500°K and 400°K is 2, if Arrhenius law is used. What will be this ratio, if transition state theory is used with the same value of „E/R‟ ?

   A. 1.6
   B. 2
   C. 2.24
   D. 2.5

5. In a reaction, the threshold energy is equal to (where, A = activation energy N = normal energy of reactants) ?

   A. A
   B. N
   C. A + N
   D. A – N

6. When the reaction occurs in the diffusion controlled region, the apparent activation energy as measured is only _______________ the true value?

   A. Twice
   B. Half
   C. Equal
   D. None of these

7. For a vapour phase catalytic reaction (A + B → P) which follows the Ridel mechanism and the reaction step is rate controlling, the rate of reaction is given by (reaction rate is irreversible, product also absorbs) ?

   A. -rA = (k . PA . PB)/(1 + KAPA + KPPP)
   B. -rA = (k . PA
   2 – k1PP)/(1 + KAPA + KPPP)
   C. -rA = (k . PA . PB)/(1 + KAPB + KBPB . KPPP)
   D. -rA = (k . PA . PB)/(1 + KAPA)

8. Rate constant for a first order reaction does not depend upon reaction time, extent of reaction and the initial concentration of reactants; but it is a function of reaction temperature. In a chemical reaction, the time required to reduce the concentration of reactant from 100 gm moles/litre to 50 gm moles/litre is same as that required to reduce it from 2 gm moles/litre to 1 gm mole/litre in the same volume. Then the order of this reaction is ?

   A. 0
   B. 1
   C. 2
   D. 3

9. A chemical reaction occurs, when the energy of the reacting molecules is ________________ the activation energy of reaction?

   A. Less than
   B. Equal to
   C. More than
   D. Equal to or more than

10. A chemical reaction occurs when the energy of the reacting molecules is __________________ the activation energy of the reaction?

    A. Less than
    B. Equal to
    C. More than
    D. Equal to or more than