Surface Chemistry

To solve the problem, we need to determine the correct thermodynamic changes (ΔG, ΔH, and ΔS) during the adsorption of a gas on the surface of a solid.

1. Understanding the Process of Adsorption:
Adsorption is the process where gas molecules adhere to the surface of a solid. This process typically occurs spontaneously under favorable conditions.

2. Analyzing the Thermodynamic Changes:
- ΔG (Gibbs Free Energy): For a process to be spontaneous, ΔG must be negative (ΔG < 0). In adsorption, the process is spontaneous, as the gas molecules are bound to the solid surface and stabilize.

- ΔH (Enthalpy Change): The adsorption process is usually exothermic, meaning heat is released as the gas molecules bind to the solid surface. Therefore, ΔH is negative (ΔH < 0).

- ΔS (Entropy Change): During adsorption, gas molecules are restricted to the surface of the solid, leading to a decrease in randomness or disorder. Therefore, ΔS is negative (ΔS < 0).

3. Conclusion:
In the adsorption of a gas on the surface of a solid, the thermodynamic changes are as follows:
ΔG < 0 (spontaneous), ΔH < 0 (exothermic), and ΔS < 0 (decrease in disorder).

Final Answer:
The correct answer is: ΔG < 0, ΔH < 0, ΔS < 0