Which of the following statements is correct for the spontaneous adsoption of a gas?

Options

A. `DeltaS` is negative and therefore, `DeltaH` should be highly positive.
B. `DeltaS` is negative and therefore, `DeltaH` should be highly negative
C. `DeltaS` is positve and therefore, `DeltaH` should be negative
D. `DeltaS` is positive and therefore, `DeltaH` should also be highly positive

Answer

B

Explanation

`DeltaS` [Change in entropy] and `DeltaH` [Change in enthalpy] are related by the equation `DeltaG=DeltaH-TDeltaS`
[Here, `DeltaG`=Change in Gibbs free energy]
For adsorption of a gas , `DeltaS` is negative because randomness decreases. Thus, in order in order to make `DeltaG` negative [for spontaneous reaction] , `DeltaH ` must be highly negative . Hence for the adsorption of a gas , if `DeltaS` is negative , therefore, `DeltaH` should be highly negative.