Ideal gas law to find moles and mass of methane

Steps:

• Convert temperature to Kelvin: T = 60 + 273 = 333 K
• Calculate moles n = PV / RT with P = 103 kPa = 103000 Pa, V = 3.57 × 10^{-2} m³, R = 8.314 Pa m³/mol K
• Perform division: n = (103000 × 0.0357) / (8.314 × 333) ≈ 0.19 mol to two sig figs
• Compute mass = n × 16 g/mol = 3 g

Why C is correct:

• Ideal gas law PV = nRT gives n = PV / RT ≈ 0.19 mol; mass = n × molar mass (16 g/mol for CH₄) = 3 g to two sig figs

Why the others are wrong:

• A. Too small; assumes V in liters without unit conversion, yielding ~0.03 g
• B. Too small; assumes wrong R value or T in °C, yielding ~0.02 g
• D. Molar mass alone; assumes n = 1 mol, ignoring PV / RT calculation

Final answer: C