Vapour density of a gas is 8. Its molecular mass will be

Options

A. 8
B. 16
C. 32
D. 64

Answer

To find the molecular mass of a gas given its vapor density, we can use the following steps:

### Step-by-Step Solution:

1. **Understand the Definition of Vapor Density**:
- Vapor density (VD) is defined as the density of the gas compared to the density of hydrogen. Mathematically, it is given by:
\[ \text{Vapor Density} = \frac{\text{Molecular Mass of the Gas}}{\text{Molecular Mass of Hydrogen (H}_2\text{)}} \]

2. **Know the Molecular Mass of Hydrogen**:
- The molecular mass of hydrogen (H₂) is 2 g/mol.

3. **Set Up the Equation**:
- From the definition, we can rearrange the equation to solve for the molecular mass of the gas (M):
\[ \text{Vapor Density} = \frac{M}{2} \]
- Therefore, we can express the molecular mass of the gas as:
\[ M = \text{Vapor Density} \times 2 \]

4. **Substitute the Given Vapor Density**:
- In this problem, the vapor density of the gas is given as 8. Substituting this value into the equation gives:
\[ M = 8 \times 2 \]

5. **Calculate the Molecular Mass**:
- Performing the multiplication:
\[ M = 16 \]

6. **Conclusion**:
- The molecular mass of the gas is 16 g/mol.

### Final Answer:
The molecular mass of the gas is **16 g/mol**.

---