The mass of 216.5 mL of a gas at S.T.P. is found to be 0.6862 g. Calculate the molecular mass of the gas. Also calculate its atomic mass if the gas is diatomic.

Explanation

To solve the problem, we will follow these steps:

### Step 1: Calculate the density of the gas.
The density (d) of a substance is calculated using the formula:
\[ d = \frac{\text{mass}}{\text{volume}} \]
Given:
...