Question

During the adsorption of reactant molecules on a catalyst surface:

• A. $△G=-ve,△H=-ve,△S=+ve$
• B. $△G=-ve,△H=-ve,△S=-ve$
• C. $△G=+ve,△H=-ve,△S=-ve$
• D. $△G=+ve,△H=+ve,△S=+ve$

Answer 1

The correct option is B $△G=-ve,△H=-ve,△S=-ve$

Adsorption is a spontaneous process therefore $△G$ is negative. As it accompanied by a decrease in randomness, $△S$ is also negative.
From the equation :
$\Delta G=\Delta H-T\Delta S$
$△H$ must be negative which concludes that adsorption an exothermic process.
Hence, the correct option is (b).