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According to the adsorption theory of catalysis, the speed of the reaction increases because :
A
The concentration of reactant molecules at the active centers of the catalyst becomes high due to adsorption
B
In the process of adsorption, the activation energy of the molecules becomes large
C
Adsorption produces heat which increases the speed of the reaction
D
Adsorption lowers the activation energy of the reaction.
Detailed Solution
According to the adsorption theory of heterogeneous catalysis, the reactant molecules are adsorbed at the active centres on the catalyst surface. The steps are: diffusion of reactants to the surface, adsorption, reaction on the surface, desorption of products and their diffusion away.
Adsorption is an exothermic process. The heat of adsorption released at the surface is taken up by the adsorbed molecules and is used in enhancing the rate of the reaction.
Adsorption also brings the reactant molecules close together at the active centres and weakens their bonds.
So, as per the answer key, the speed of the reaction increases because adsorption produces heat, which increases the speed of the reaction. (Adsorption raising the surface concentration of reactants and lowering the activation energy are also part of the same theory; the answer key picks the heat of adsorption.)
Adsorption is an exothermic process. The heat of adsorption released at the surface is taken up by the adsorbed molecules and is used in enhancing the rate of the reaction.
Adsorption also brings the reactant molecules close together at the active centres and weakens their bonds.
So, as per the answer key, the speed of the reaction increases because adsorption produces heat, which increases the speed of the reaction. (Adsorption raising the surface concentration of reactants and lowering the activation energy are also part of the same theory; the answer key picks the heat of adsorption.)