Calculate the density in grams per liter of a gas at STP if

Calculate the density, in grams per liter, of a gas at STP if 3.22 L of the gas at 35.9 °C and 743.5 mm Hg weighs 0.868 g.

We have volume of gas at 35.9 ^oC and 743.5 mmHg = 3.22 L

STP is 273 K temperature and 760 mmHg pressure

35.9 oC = 35.9 + 273 = 308.9 K

for any ideal gas at in a closed container

P1V1/T1 = P2V2/T2

743.5 mmHg x 3.22 L / 308.9K = 760 mmHg x V2 / 273K

V2 = 2.784 L

denisty = mass / volume = 0.868g / 2.784 L = 0.312 g/L