Adsorption is accompanied by the evolution of heat. Thus, according to Le Chatelier's principle the amount of surface adsorbed should
(i) decrease with increase in temperature
(ii) decrease with decrease in temperature
(iii) increase with increase in temperature
(iv) increase with decrease in temperature

Options

A. increase with decrease in temperature
B. increase with increase in temperature
C. decrease with decrease in temperature
D. be equal at all temperature

Explanation

To solve the question regarding the effect of temperature on adsorption according to Le Chatelier's principle, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Adsorption**:
- Adsorption is the process where molecules from a gas or liquid adhere to a solid surface. This process is typically exothermic, meaning it releases heat.

2. **Applying Le Chatelier's Principle**:
- Le Chatelier's principle states that if a system at equilibrium is subjected to a change in temperature, pressure, or concentration, the system will adjust itself to counteract that change and restore a new equilibrium.

3. **Identifying the Nature of the Process**:
- Since adsorption is an exothermic process (it releases heat), if the temperature of the system increases, the equilibrium will shift to favor the reactants (the gas phase) to absorb the excess heat. This means that less gas will be adsorbed onto the surface at higher temperatures.

4. **Analyzing the Options**:
- (i) Decrease with increase in temperature: This is consistent with our understanding, as higher temperatures would lead to less adsorption.
- (ii) Decrease with decrease in temperature: This is not correct; lower temperatures favor adsorption.
- (iii) Increase with increase in temperature: This contradicts our analysis; higher temperatures lead to less adsorption.
- (iv) Increase with decrease in temperature: This aligns with our understanding; lower temperatures favor more adsorption.

5. **Conclusion**:
- Based on the analysis, the correct answer is (iv) increase with decrease in temperature. As the temperature decreases, more gas molecules will be adsorbed onto the surface due to the exothermic nature of the process.

### Final Answer:
The amount of surface adsorbed should **increase with decrease in temperature**.

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