Question

The molar mass of a gas with a density of 5.8 g/L at ${25}^0$C and 740 mm Hg is closest to:

• A. 20 g/mol
• B. 10 g/mol
• C. 146 g/mol
• D. 190 g/mol

Answer 1

The correct option is C 146 g/mol

$M=\frac{dRT}{P}$

$M=\frac{\text{5.8 g/L}\times \text{0.08206 L atm/mol/K}\times [25+\text{273 K}]}{\text{740 mm Hg}\times \frac{\text{1 atm}}{\text{760 mm Hg}}}$
$M=\text{145.6 g/mol}$

The molar mass of the gas is $\text{146 g/mol}$