A 3.15 gram sample of an unknown gas is found to occupy a volume of 2.22 L at a pressure of 519 mmHg and a temperature of 34°C. Assume ideal behavior. The molecular weight of the unknown gas is?

1 Answer
anor277
Oct 15, 2017

#"Molecular mass"~=100*g*mol^-1#

Explanation:

To key to answering these questions is TO KNOW that #1*atm# of pressure will support a column of mercury that is #760*mm# high. A mercury column is thus a very convenient means to measure pressure that is near or below atmospheric.

And so we gots a pressure of #(519*mm*Hg)/(760*mm*Hg*atm^-1)=0.683*atm#.

And so we fill in the dots......

#n="mass"/"molar mass"=(PV)/(RT)#

And #"molar mass"=("mass"xxRT)/(PV)#

#=(3.15*gxx0.0821*L*atm*K^-1*mol^-1xx307*K)/(0.683*atm)#

#=??*g*mol^-1#

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