Chemistry
posted by Coug .
What is the molecular weight of a gas if a 15.0g sample has a pressure of 836 mm Hg at 25.0 degrees C in a 2.00 L flask?
a)167
b)1.35
c)176
d)11.1
e)none of the above
Please explain... I need to understand how to do this. Thanks.

Use PV = nRT to solve for n.
Then n = grams/molar mass. 
I'm still confused... I know that:
P=1.1 atm
V=2.00 L
n=?
R= I think .0821
and
T= ?
I have no idea how to change 15.0g to moles, since I do not know what the element is to look at the atomic massI know that one mole is avagadro's number, but I'm still really not sure what to do here.
Please help...