If relative molecular mass of a gas is 38, what will be its vapour density ?

Options

A. 76
B. 19
C. 40
D. zero

Explanation

To find the vapor density of a gas given its relative molecular mass, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of Vapor Density**:
Vapor density is defined as the mass of a certain volume of gas compared to the mass of an equal volume of hydrogen gas at the same temperature and pressure. Mathematically, it can be expressed as:
\[ \text{Vapor Density} = \frac{\text{Molar Mass of the Gas}}{2} \]
This is because the molar mass of hydrogen (H₂) is approximately 2 g/mol.

2. **Identify the Given Information**:
The problem states that the relative molecular mass of the gas is 38.

3. **Apply the Formula**:
Now, we can substitute the given relative molecular mass into the formula for vapor density:
\[ \text{Vapor Density} = \frac{38}{2} \]

4. **Calculate the Vapor Density**:
Performing the division:
\[ \text{Vapor Density} = 19 \]

5. **Conclusion**:
Therefore, the vapor density of the gas is 19.

### Final Answer:
The vapor density of the gas is 19.

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