To answer this item, it is assumed that methane behaves ideally such that it follows the equation,
PV = nRT
where P is pressure, V is volume, R is the universal gas constant, and T is temperature. Solving for the value of n,
n = PV / RT
At STP condition, T is equal to 0°C (273.15 K) and P is equal to 1 atm. Substituting the known values,
n = (1 atm)(10 L) / (0.0821 L.atm/mol.K)(273.15 K)
n = 0.446 mol
Then, multiply the number of moles by the molar mass of methane, 16 g/mol.
M = (0.446 mol)(16 g/mol) = 7.13 g
ANSWER: 7.13 g
