Rate of diffustion of a gas is :

Options

A. directly proportional to its density
B. directly proportional to its molecular mass
C. directly proportional to the square root of its molar mass
D. inversely propertional to the squaure root of its molar mass.

Explanation

To solve the question regarding the rate of diffusion of a gas, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Diffusion**:
- Diffusion is the process by which gas molecules spread from an area of higher concentration to an area of lower concentration. The rate of diffusion can be influenced by various factors.

2. **Identify the Relevant Law**:
- The rate of diffusion of a gas is described by Graham's Law of Effusion, which states that the rate of effusion (or diffusion) of a gas is inversely proportional to the square root of its molar mass.

3. **Establish the Relationship**:
- According to Graham's Law:
\[ \text{Rate of diffusion} \propto \frac{1}{\sqrt{\text{Molar Mass}}} \]
- This means that as the molar mass of a gas increases, the rate of diffusion decreases.

4. **Analyze the Options**:
- Option 1: Directly proportional to its density (Incorrect)
- Option 2: Directly proportional to its molecular mass (Incorrect)
- Option 3: Directly proportional to the square root of its molar mass (Incorrect)
- Option 4: Inversely proportional to the square root of its molar mass (Correct)

5. **Conclusion**:
- Based on the analysis, the correct answer is that the rate of diffusion of a gas is inversely proportional to the square root of its molar mass. Therefore, the answer is **Option 4**.