The molecular formula of butane is C₄H₁₀
Thus the molar mass of butane = 4 X 12 + 10 X 1 = 58 g/mol
According to Avagadro's law: the volume of an ideal gas is directly proportional to the moles of the gas molecules
Or
at STP (standard Temperature and pressure, 298K and 1atm)
The volume occupied by one mole of a gas is 22.4 L
thus the moles of butane occupying 22.4L of volume =1 mol
the mass of each mole of butane = 58g
Thus the mass of butane needed to occupy a volume of 22.4L at STP = 58g