calculate the molecular weight of a gas if under STP conditions its density is 1.4 g/L

Answer 1

At STP, gases are 22.4L/ mol

So start with the density 1.4g/L. If we want g/mol (the molecular weight), then we can just multiply the density by 22.4L/mol

1.4g/L x 22.4L/ mol = 31.36g/ mol.

The liters cancel out giving us units of g/mol.