Question

A glass vessel weighs $50$ g when empty, $148.0$ g when completely filled with liquid of density $0.98g{ml}^{-1}$ and $50.5$ g when filled with an ideal gas at $760$ mm of Hg at $300$ K. Determine the molecular weight of the gas.

• A. 183 g/mol
• B. 143 g/mol
• C. 123 g/mol
• D. 150 g/mol

Answer 1

The correct option is C 123 g/mol

Volume of container $=\frac{massofliquid}{density}=\frac{148.0-50}{0.98}=100ml=0.1L$.

Mass of gas $=50.5-50=0.5g$.

The molecular weight can be calculated from the ideal gas equation which is,

$PV=\frac{W}{M}\times RT$

$1atm\times 0.1L=\frac{0.5g}{M}\times 0.082Latmmo{l}^{-1}{K}^{-1}\times 300K$

Thus, the molecular weight of the gas is $123$ g/mol.