How to Calculate the Molar Mass of an Unknown Gas?

[momen1981]

Given the following data for a gas, use the equation for the ideal gas law to calculate the molar mass.

Mass = 0.810 g
Pressure = 0.954 atm
Volume = 0.461 L
Temp = 291 K


M = mRT/PV = 44.0?

 

[BlackHole213]

I won't give you the answer but the following is how you solve the equation

PV=nRT

P=pressure (0.954 atm [use kpa since that is what is required in the ideal gas law thus pressure is 0.954*101.325 kpa = 96.66405 kpa])

V=volume (0.461 L)

R=Universal gas constant or 8.314

T=temperature (291 K)

m=mass (0.810 g)

n=mol (unknown)

M=molar mass (unknown)

PV=nRT which becomes

n=PV/RT

After you get mols, use this formula n=m/M or M=n*m

 

[momen1981]

OK I understand now -- thank you!