Chemistry
posted by Ashley .
A helium baloon has a volume of 28.9L, what is the mass of helium inside the ballon? what is the mass of the same volume of air it displaces? MM of air = 29.0g/mol, 25C (temperature) and 1 atm.

Use PV = nRT and solve for n = moles He. then moles = grams/molar mass. Solve for grams He.
mass air = moles air x molar mass air.