Question

(4) An unknown gas occupies a volume of 4.75 L at 1500 K and 5.00 atm. If its mass is 5.45 g, what is the molar mass of the gas? Hint: molar mass = dRT/P.

Answer 1

We have given the volume V = 4.75 L

Pressure = 5 atm

Mass in gram = 5.45 gram

R = 0.02821 atmL/molK

Temperature T =1227°C=1227+273=1500 K

From ideal gas equation PV=nRT

$5\times 4.75=n\times 0.0821\times 1500$

$5×4.75=n×0.0821×1500$

n=0.1928

So molar mass $\frac{mass\ in\ gram}{n}=\frac{5.45}{0.1928}=28.25g/mol$