If a 0.614 g sample of a gas maintains a pressure of 238 mm hg when contained in a 1.0 l flask at 0.0°c, what is the gas's molecular weight?

To determine the molecular weight, we need an equation to relate the molecular weight and the given conditons in the problem statement. Molecular weight is the mass of the mass per one mole of it. For a gas, we can assume ideal gas and use the equation PV=nRT. We need to determine the number of moles present of the gas molecules. We do as follows:

PV = nRT
     n = M / MW
PV = (M/MW) RT
MW = MRT / PV
MW = (0.614 g) ( 0.08205 L - atm / mol - K) ( 273.15 K ) / (238 / 760 atm) ( 1.0 L )
MW = 43.94 g / mol

Therefore, the molecular weight of the gas is 43.94 g/mol.