Question

Fruend and Long were 2 scientists interested in adsorption.
Once in a discussion Fruend asked "I can see adsorption is spontaneous, but why it is always exothermic?"
Long said"_________________"
Choose Long's answer :

• A. $△$G > 0 & $△$ S < 0 $\Rightarrow$ $△$H < 0
• B. $△$G < 0 & $△$ S < 0 $\Rightarrow$ $△$H < 0
• C. $△$G > 0 & $△$ S > 0 $\Rightarrow$ $△$H > 0
• D. $△$G , 0 & $△$ S > 0 $\Rightarrow$ $△$H > 0

Answer 1

The correct option is B $△$G < 0 & $△$ S < 0 $\Rightarrow$ $△$H < 0

For the adsorption-

$\Delta G,\Delta H,\Delta S$ all are negative.

According to Gibbs free energy-

$\Delta G=\Delta H-T\Delta S$

$\Delta G=\Delta H+T\Delta S$, as the $\Delta S=-ve$

So $\Delta H=\Delta G-T\Delta S$

As the $\Delta G$ is already negative so $\Delta H$ also comes negative.