Question

In adsorption, the thermodynamic requirement is:

• A. \(\Delta H = +ve\); \(\Delta S = +ve\)
• B. \(\Delta H = -ve\); \(\Delta S = -ve\)
• C. \(\Delta H = -ve\); \(\Delta S = +ve\)
• D. \(\Delta H = +ve\); \(\Delta S = -ve\)

Hint:

Adsorption is generally exothermic and decreases entropy of the system.

Answer 1

The Correct Option is B

Step 1: Enthalpy signature.
Adsorption liberates heat, making ΔH negative.

Step 2: Entropy signature.
Gaseous molecules become confined to a surface, decreasing disorder, so ΔS is negative.

Step 3: Final deduction.
The thermodynamic condition is ΔH = -ve, ΔS = -ve.