Rate of physisorption increases with 

Options

A. Decrease in temperature
B. Increase in temperature
C. Decrease in pressure
D. Decrease in surface area

Answer

To solve the question regarding the factors affecting the rate of physisorption, we will analyze each option provided in the question step by step.

### Step-by-Step Solution:

1. **Understanding Physisorption**:
- Physisorption is a type of adsorption where the adsorbate is held to the adsorbent by weak van der Waals forces. It is generally reversible and depends on various factors including temperature, pressure, and surface area.

2. **Effect of Temperature**:
- As temperature increases, the kinetic energy of the molecules also increases. This leads to a greater likelihood of desorption (the process where adsorbed molecules leave the surface). Therefore, the rate of physisorption decreases with increasing temperature.
- Conversely, decreasing the temperature allows for more molecules to be adsorbed, as the kinetic energy is lower, leading to a higher rate of physisorption.

3. **Effect of Pressure**:
- Increasing the pressure of the gas phase increases the number of gas molecules available to collide with the surface of the adsorbent. This results in an increased rate of physisorption.
- Thus, the rate of physisorption increases with increasing pressure.

4. **Effect of Surface Area**:
- The greater the surface area of the adsorbent, the more sites are available for adsorption. This directly correlates with an increased rate of physisorption.
- Therefore, the rate of physisorption increases with increasing surface area.

5. **Analyzing the Options**:
- **Option A (Decreasing Temperature)**: This is correct as the rate of physisorption increases with decreasing temperature.
- **Option B (Increasing Temperature)**: This is incorrect as the rate of physisorption decreases with increasing temperature.
- **Option C (Decreasing Pressure)**: This is incorrect as the rate of physisorption increases with increasing pressure.
- **Option D (Decreasing Surface Area)**: This is incorrect as the rate of physisorption increases with increasing surface area.

### Conclusion:
The correct answer is **Option A: Decreasing Temperature**.