AP EAMCET20228 Jul 2022Evening ShiftChemistrySurface ChemistryActual
Assertion (A) Adsorption is an exothermic process. Reason (R) Physisorption of a gas on a solid surface is normally reversible.
Options
- ABoth A and R are correct and R is the correct. explanation of A .
- BBoth A and R are correct but R is not the correct explanation of A .
- CA is correct but R is incorrect.
- DA is incorrect but R is correct.
Correct answer
B. Both A and R are correct but R is not the correct explanation of A .
Step-by-step solution
Both Assertion and Reason are correct but Reason is not the correct explanation of Assertion. The correct reason for given assertion is as follows : When a gas is adsorbed on a solid surface, its movement is restricted. This leads to a decrease in the entropy of the gas i.e. S is negative. Now, for a process to be spontaneous, G should be negative. We know that, G= H-T S Now, S is negative, H has to be negative to make G negative. Hence, adsorption is always exothermic.