Ideal gas law to find methane sample mass

Steps:

• Convert temperature to Kelvin using T(K) = T(°C) + 273: 60 + 273 = 333 K
• Convert volume to liters for consistent units with R: 3.57 × 10^{-2} m³ × 1000 L/m³ = 35.7 L
• Calculate moles n = (P × V) / (R × T) with P = 103 kPa, R = 8.314 L kPa/mol K
• Calculate mass m = n × 16 g/mol (molar mass of CH₄)

Why C is correct:

• PV = nRT gives n = 0.187 mol; m = 0.187 mol × 16 g/mol = 3 g exactly by the ideal gas law.

Why the others are wrong:

• A. 0.032 g: From misusing volume as 0.357 L, yielding smaller n ≈ 0.013 mol.
• B. 0.018 g: From treating V = 0.0357 L and using C atomic mass 12 g/mol, yielding n ≈ 0.0015 mol.
• D. 16 g: From assuming n = 1 mol without calculating PV/RT.

Final answer: C