What is The molar mass of the gas if its density is 22.4 g per leaders at Stp

STP means standard temperature and pressure at 0°C (273K) and 1 atm (atmosphere). The density of the unknown gas is 22.4 gram per liter. The deal gas equation is PV = nRT. The n is the number of moles and can be represented as mass of the gas, m, divided by the molar mass, c.  so we have,   PV = nRT PV = (m/c)RT Since the density is d = m/V Pc = (m/V)RT Pc = dRT c = drT/P   substitute the values into the equation, c = [(22.4g/L)(0.08206 L-atm/mol-K)(273K)]/(1atm) c = 501.8 g/mol