ideal gas law PV = nRT or PM = dRt ( M is molecular mass of gas ) and d is gas density
where m/ M ( m is mass of gas sample )
m = dRT / P ( 2.78 g/L ) ( 0.082 L atm/ K mole )( 310K ) / 1.2 atm =
58.9 g/mol
gas must be butane ( C4H10) has molecular mass = 58.9 g/mol
