A,B and C are ideal gases. Their molecular weights are 2,4 and 28 respectively. The rate of diffusion of these gases follow the order

Options

A. `C gt A gt B`
B. `C gt B gt A`
C. `A = B=C`
D. `A gt B gt C`

Explanation

To solve the problem of determining the order of diffusion rates for the gases A, B, and C based on their molecular weights, we can use Graham's law of effusion, which states that the rate of diffusion of a gas is inversely proportional to the square root of its molar mass (molecular weight).

### Step-by-Step Solution:

1. **Identify the Molecular Weights**:
- Gas A has a molecular weight of 2 g/mol.
- Gas B has a molecular weight of 4 g/mol.
- Gas C has a molecular weight of 28 g/mol.

2. **Apply Graham's Law**:
Graham's law states that:
\[ \text{Rate of diffusion} \propto \frac{1}{\sqrt{\text{Molar mass}}} \]
This means that a gas with a lower molar mass will diffuse faster than a gas with a higher molar mass.

3. **Calculate the Rates of Diffusion**:
- For Gas A:
\[ \text{Rate}_A \propto \frac{1}{\sqrt{2}} \approx 0.707 \]
- For Gas B:
\[ \text{Rate}_B \propto \frac{1}{\sqrt{4}} = 0.5 \]
- For Gas C:
\[ \text{Rate}_C \propto \frac{1}{\sqrt{28}} \approx 0.189 \]

4. **Compare the Rates**:
- From the calculations:
- Rate of diffusion of A (0.707) is the highest.
- Rate of diffusion of B (0.5) is in the middle.
- Rate of diffusion of C (0.189) is the lowest.

5. **Order of Diffusion**:
Based on the rates calculated, the order of diffusion from highest to lowest is:
\[ \text{A} > \text{B} > \text{C} \]

### Final Answer:
The order of diffusion of the gases A, B, and C is A > B > C.