what is the molor mass (grams/mole) of a gas if 2.25 grams of it occupies 3.50 l at STP?
mols = n = 3.50L x (1 mol/22.4L) = ?
n = grams/molar mass. You know mols and grams, solve for molar mass.
n = grams/molar mass. You know mols and grams, solve for molar mass.