Question

Which one of the following characteristic is associated with adsorption?

• A. $△G$ is negative but $△H$ and $△S$ are positive
• B. $△G,△H$ and $△S$ all are negative
• C. $△G$ and $△H$ are negative but $△S$ is positive
• D. $△G$ and $△S$ are negative but $△H$ is positive

Answer 1

The correct option is B $△G,△H$ and $△S$ all are negative

For adsorption, $△G,△H$ and $△S$ all are negative. Adsorption is a spontaneous process therefore change in free energy for the process is negative. Since adsorption is exothermic in nature, the enthalpy change is negative. The entropy change is negative because the adhering of gas molecules to the surface lowers randomness.

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