Spontaneous adsorption of a gas on solid surface is an exothermic process because

Options

A. `DeltaH` increase for system
B. `DeltaS` increases for gas
C. `DeltaH` decreases for gas
D. `DeltaG` increases for gas

Answer

C

Explanation

For spontaneous adsorption process, standard Gibbs's energy free energy `(DeltaG)`, must be negative as well as the degree of randomnes of gas moleucle on the surface of solid decreases. For exothermic process, `DeltaH` must be negative. Hence, with the help of following equation.
`DeltaH = DeltaG + T.DeltaS`
`T.DeltaS` is negative. Thus, during adsorption `DeltaS` decreases
As, we know that `DeltaG = DeltaH - TDeltaS`