The mass of 800cm3 of a gas X at s.t.p. is 1.0g. What is the…

The mass of 800cm³ of a gas X at s.t.p. is 1.0g. What is the molar mass of X? [1 mole of a gas at s.t.p occupies 22.4dm ³]

The correct answer is: C

The mass of 0.8dm³ of a gas at s.t.p. is 1.0g :. 22.4dm> of gas at s.t.p. will have a molar mass of 22.4/0.8 = 28.0g mol^-1