Which of the following is less than zero during adsorption?

Options

A. `DeltaG`
B. `DeltaS`
C. `DeltaH`
D. All of these.

Answer

To determine which of the given thermodynamic quantities is less than zero during adsorption, we will analyze each option: ΔG (Gibbs free energy change), ΔS (entropy change), and ΔH (enthalpy change).

### Step-by-Step Solution:

1. **Understanding Adsorption**:
- Adsorption is the process where molecules adhere to a surface. It is generally considered a spontaneous process.

2. **Analyzing ΔG (Gibbs Free Energy Change)**:
- The Gibbs free energy change (ΔG) for a spontaneous process is always less than zero.
- Mathematically, ΔG = ΔH - TΔS.
- For adsorption to be spontaneous, ΔG must be negative, indicating that the process occurs without external energy input.

3. **Analyzing ΔS (Entropy Change)**:
- Entropy (ΔS) is a measure of disorder in a system.
- During adsorption, the randomness of the system decreases because gas molecules become localized on the surface of the adsorbent.
- Therefore, ΔS is typically negative for adsorption processes.

4. **Analyzing ΔH (Enthalpy Change)**:
- Enthalpy change (ΔH) during adsorption is usually negative because the process is exothermic. This means that energy is released when the adsorbate molecules adhere to the surface.
- Thus, ΔH < 0 for most adsorption processes.

5. **Conclusion**:
- All three quantities (ΔG, ΔS, ΔH) are less than zero during adsorption.
- Therefore, the correct answer is **D: All of the above**.