Physical adsorption is considerable at

Options

A. low temperature
B. room temperature
C. high temperature
D. none of these

Explanation

To determine the conditions under which physical adsorption is considerable, we need to analyze the thermodynamics involved in the process. Here’s a step-by-step solution to the question:

### Step 1: Understand Physical Adsorption
Physical adsorption, also known as physisorption, occurs due to weak Van der Waals forces between the adsorbate (the substance being adsorbed) and the adsorbent (the surface on which adsorption occurs).

**Hint:** Remember that physical adsorption is characterized by weak interactions compared to chemical adsorption.

### Step 2: Analyze the Thermodynamics
In physical adsorption, the change in enthalpy (ΔH) is negative because the process is exothermic. This means that heat is released when the adsorbate adheres to the adsorbent.

**Hint:** Exothermic processes release heat, leading to a negative ΔH.

### Step 3: Consider the Change in Entropy
The change in entropy (ΔS) for physical adsorption is also negative. This is because the adsorbate molecules become more ordered when they adhere to the surface of the adsorbent.

**Hint:** A decrease in disorder (or increase in order) corresponds to a negative change in entropy.

### Step 4: Apply Gibbs Free Energy Equation
For a process to be spontaneous, the change in Gibbs free energy (ΔG) must be negative. The relationship is given by:
\[ \Delta G = \Delta H - T \Delta S \]

Since ΔH is negative and ΔS is also negative, the term \( -T \Delta S \) becomes positive. Therefore, for ΔG to be negative, ΔH must be more negative than \( T \Delta S \).

**Hint:** A more negative ΔH at lower temperatures helps ensure that ΔG remains negative.

### Step 5: Determine the Effect of Temperature
At low temperatures, the value of \( T \Delta S \) is smaller because T is low. This means that the negative ΔH can dominate, making ΔG negative and thus making the process spontaneous.

**Hint:** Lower temperatures favor the spontaneity of physical adsorption by reducing the impact of the positive \( T \Delta S \) term.

### Conclusion
Based on the analysis, physical adsorption is considerable at **low temperatures**. This is because lower temperatures allow for a more negative ΔH to dominate over the positive \( T \Delta S \), ensuring that ΔG remains negative and the process is spontaneous.

**Final Answer:** Low temperature