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?

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.I know that I have to use PV=nRT, then solve for n grams/molar massAnd, 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 mass–I know that one mole is avagadro’s number, but I’m still really not sure what to do here. Please help…