Which of the following statements of 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 positive 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 to make `DeltaG` negative [for spontaneous reaction]. `DeltaH` must be highly negative because reaction is exothermic. Hence, for the adsorption of a gas, if `DeltaS` is negative, therefore, `DeltaH` should be highly negative, therefore, `DeltaH` should be highly negative.