A first order reaction A → B occurs in an isothermal porous catalyst pellet of spherical shape. If the concentration of A at the centre of the pellet is much less than at the external surface, the process is limited by

A first order gaseous phase reaction is catalysed by a non-porous solid. The kinetic rate constant and the external mass transfer co-efficients are k and $${{\text{k}}_{\text{g}}}$$ respectively. The effective rate constant (k_eff) is given by

A. $${{\text{k}}_{\text{e}}}{\text{ff}} = {\text{k}} + {{\text{k}}_{\text{g}}}$$

B. $${{\text{k}}_{\text{e}}}{\text{ff}} = \frac{{{\text{k}} + {{\text{k}}_{\text{g}}}}}{2}$$

C. $${{\text{k}}_{\text{e}}}{\text{ff}} = {\left( {{\text{k}}{{\text{k}}_{\text{g}}}} \right)^{\frac{1}{2}}}$$

D. $$\frac{1}{{{{\text{k}}_{\text{e}}}{\text{ff}}}} = \frac{1}{{\text{k}}} + \frac{1}{{{{\text{k}}_{\text{g}}}}}$$

The half life period of a first order reaction is given by (where, K = rate constant. )

A. 1.5 K

B. 2.5 K

C. $$\frac{{0.693}}{{\text{K}}}$$

D. 6.93 K

Catalyst is a substance, which __________ chemical reaction.

A. Increases the speed of a

B. Decreases the speed of a

C. Can either increase or decrease the speed of a

D. Alters the value of equilibrium constant in a reversible

A chemical reaction is of zero order, when the reaction rate is (where, CA = concentration of reactant)

A. $$ \propto {\text{CA}}$$

B. $$ \propto \frac{1}{{{\text{CA}}}}$$

C. Independent of temperature

D. None of these