chemistry
posted by kendra .
0.82g of an unknown gass is at 30 degrees C in 3L container at a pressure of 15.9psi. What is the molecular weight of the unknown gas?

Convert 15.9 psi to atm, then use PV = nRT and solve for n = number of mols.
Then n = grams/molar mass. You know n and grams, solve for molar mass. 
ok so i have 1.08atm(3L)=nR(303.2k) then what do i do?

I find 1.021 atm = 15 psi.
R = 0.08206 = universal gas constant. Memorize this. You'll use it a lot with gas laws.
Solve for n
Then n = 0.82/molar mass
Solve for molar mass. 
6.3mm

I obtained a slightly different value because I used 1.02 atm for 15 psi.

It was 15.9psi so my answer will be a little different. thanks for your help!

I can't read, can I?