A gas occupies 700 `cm^(3)` at a pressure of 700 mm of Hg and a temperature of -57°C . If, at S.T.P., the mass of the gas is 1.5 g, find the vapour density and the molecular mass of the gas. Given l litre of hydrogen weighs 0.09 g at S.T.P.

Explanation

To solve the problem, we will follow these steps:

### Step 1: Convert the given values to appropriate units
- **Volume (V)**: 700 cm³ = 700 × 10⁻³ L = 0.7 L
- **Pressure (P)**: 700 mm of Hg = 700 / 760 atm = 0.9211 atm
- **Temperature (T)**: -57°C = 273 - 57 = 216 K

### Step 2: Use the Ideal Gas Law to find the number of moles (n)
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