What is the molar mass of a gas if 3.50 grams of the gas occupy 1.35 liters of space at STP

A. 8.64 g/mol
B. 58.1 g/mol
C. 78.4 g/mol
D. 106 g/mol

The ideal gas law can be rearranged to give

PM = dRT

P = gas pressure in atm = 1.00 atm (STP)
M = molar mass in g/mole
d = gas density in g/L = 3.50 / 1.35 = 2.59
R = gas constant = 0.0821 L atm / K mole
T = Kelvin temperature = 273 K (STP)

M = dRT / P = (2.59)(0.0821)(273) / (1.00) = 58.1 g/mole