Ideal Gas law and mole conversions

[Cfem]

Homework Statement

You have several identical balloons. You experimentally determine that a balloon will break if its volume exceeds 0.900L . The pressure of the gas inside the balloon equals air pressure (1.00 atm). The air inside the balloon has a constant temperature of 22 C. How many grams of oxygen can be blown into the balloon before it explodes? Helium?

Homework Equations

.9L = .0009m^3
22C = 295.15
1 atm = 1.013 x 10^5
PV = nRT

The Attempt at a Solution

(1.013 x 10^5)(.0009) = n(8.31)(295.15)
n = .03717 moles

.03717 moles = .593 grams of oxygen

I don't know if I've forgotten something with chemistry or I've missed something in the calculation, but that answer's being spit out as incorrect (automated grading). Obviously I can't do the helium part until I figure out what's wrong with this part.

Thanks.

 

[ehild]

Hi Cfem,

Oxygen is a two-atomic gas, two atoms make a molecule, its molar mass is 32 g/mol. But helium is noble gas, its molar mass equals the atomic mass.

ehild