Homework Help: Chemistry

Posted by Coug on Sunday, January 3, 2010 at 12:05pm.

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.

Chemistry - DrBob222, Sunday, January 3, 2010 at 1:48pm
Use PV = nRT to solve for n.
Then n = grams/molar mass.
Chemistry - coug--confused, Sunday, January 3, 2010 at 6:22pm
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 mass--I know that one mole is avagadro's number, but I'm still really not sure what to do here.

Please help...

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