1. The problem is to calculate the mass of a gas given certain conditions. 2. The formula to calculate the mass of a gas is derived from the ideal gas law: $$PV = nRT$$ where $P$ is pressure, $V$ is volume, $n$ is number of moles, $R$ is the ideal gas constant, and $T$ is temperature in Kelvin. 3. To find the mass $m$, use the relation $$m = nM$$ where $M$ is the molar mass of the gas. 4. From the ideal gas law, solve for $n$: $$n = \frac{PV}{RT}$$. 5. Substitute $n$ into the mass formula: $$m = \frac{PV}{RT} \times M$$. 6. Important rules: ensure pressure $P$ is in pascals (Pa), volume $V$ in cubic meters (m³), temperature $T$ in kelvin (K), and molar mass $M$ in kilograms per mole (kg/mol) or grams per mole (g/mol) consistent with units. 7. Example: If $P=100000$ Pa, $V=0.01$ m³, $T=300$ K, and $M=0.028$ kg/mol (for nitrogen), then $$m = \frac{100000 \times 0.01}{8.314 \times 300} \times 0.028 = 0.0112 \text{ kg}$$. 8. This method calculates the mass of the gas using measurable physical properties and constants.