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NEET CHEMISTRYThermodynamicsMedium

Question

Adsorption of gases on a solid surface is generally exothermic because

A

Enthalpy is positive

B

Entropy decreases

C

Entropy increases

D

Free energy increase

Step-by-Step Solution

When a gas is adsorbed on a solid surface, the movement of the gas molecules becomes restricted. This leads to a decrease in the randomness or disorder of the system, meaning the entropy decreases (ΔS\Delta S is negative). For a process to be spontaneous, the Gibbs free energy change (ΔG=ΔHTΔS\Delta G = \Delta H - T\Delta S) must be negative. Since ΔS\Delta S is negative, the term TΔS-T\Delta S becomes positive. To make the overall ΔG\Delta G negative, the enthalpy change (ΔH\Delta H) must be negative, which means the process must be exothermic. Thus, adsorption is generally exothermic because entropy decreases.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Thermodynamics. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYThermodynamicsadsorptionsurfacegenerallyexothermicbecause

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