Adsorption is accompanied by:

Options

A. decrease in entropy of the system
B. decrease in enthalpy of the system
C. T`Delta`S for the process is negative
D. All of these

Answer

To answer the question "Adsorption is accompanied by:", we will analyze the characteristics of adsorption and the changes that occur during this process.

### Step-by-Step Solution:

1. **Understanding Adsorption**:
- Adsorption is the process where gas, liquid, or dissolved solid particles (called adsorbates) accumulate on the surface of a solid or liquid (called adsorbent). This is different from absorption, where the particles penetrate into the bulk of the material.

2. **Entropy Change**:
- When adsorption occurs, the randomness or disorder of the system decreases. For example, if gas particles are adsorbed onto a solid surface, they lose their freedom of movement and become more ordered. This results in a decrease in entropy (ΔS < 0).

3. **Enthalpy Change**:
- During the adsorption process, energy is released as the adsorbate particles stick to the adsorbent surface. This release of energy indicates that the enthalpy of the system decreases (ΔH < 0). The process can be either physical (weak Van der Waals forces) or chemical (strong chemical bonds), but in both cases, energy is released.

4. **Gibbs Free Energy**:
- The change in Gibbs free energy (ΔG) for the adsorption process can be expressed as ΔG = ΔH - TΔS. Since ΔS is negative and ΔH is also negative, the term TΔS will be positive, making ΔG negative. This indicates that the adsorption process is spontaneous.

5. **Conclusion**:
- Therefore, adsorption is accompanied by a decrease in entropy, a decrease in enthalpy, and a negative Gibbs free energy change. Hence, the correct answer to the question is that adsorption is accompanied by all of these changes.

### Final Answer:
Adsorption is accompanied by a decrease in entropy, a decrease in enthalpy, and a negative Gibbs free energy change.

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