If `Cl_(2)` gas is enclosed in presence of powdered charcoal in a closed vessel, the pressure of the gas decreases. It is because :

Options

A. the gas molecules are adsorbed at the surface
B. the gas molecules concentrate at the surface of the charcoal
C. the gas molecules are adsorbed at the surface
D. the gas molecules are desorbed by the surface

Explanation

To solve the question regarding the decrease in pressure of chlorine gas (Cl₂) when it is enclosed in a closed vessel with powdered charcoal, we can follow these steps:

### Step 1: Understand the System
We have Cl₂ gas in a closed vessel along with powdered charcoal. The system is closed, meaning no gas can escape, and we need to analyze what happens to the pressure of Cl₂ gas.

**Hint:** Consider the properties of gases and how they interact with solid surfaces.

### Step 2: Recognize Adsorption
When Cl₂ gas is in contact with powdered charcoal, the gas molecules can be adsorbed onto the surface of the charcoal. Adsorption is a surface phenomenon where gas molecules adhere to the surface of a solid.

**Hint:** Think about how gas molecules behave when they come into contact with a solid surface.

### Step 3: Effect of Adsorption on Pressure
As Cl₂ gas molecules are adsorbed onto the surface of the charcoal, the number of free gas molecules in the vessel decreases. Since pressure is directly related to the number of gas molecules present in a given volume, the decrease in the number of free Cl₂ molecules leads to a decrease in pressure.

**Hint:** Remember the relationship between the number of gas molecules and pressure in a closed system.

### Step 4: Conclusion
The pressure of the gas decreases because the Cl₂ gas molecules are being adsorbed onto the surface of the powdered charcoal, thus reducing the number of gas molecules in the vessel.

**Hint:** Summarize the process: adsorption leads to fewer gas molecules, resulting in lower pressure.

### Final Answer
The pressure of Cl₂ gas decreases because the gas molecules are adsorbed at the surface of the powdered charcoal.