Question

The mass of 94.5 ml of a gas at S.T.P. is found to be 0.2231 g. Calculate its molecular mass.

Answer 1

Given:-

Mass of gas= $0.2231g$

Volume of gas at S.T.P= $94.5ml=94.5\times {10}^{-3}$ litre or $d{m}^3$

To find:- Molecular mass

Solution:-

$\frac{VolumeoccupiedbygasatSTPind{m}^3}{22.4d{m}^3}$=Number of moles

$\Rightarrow \frac{94.5\times {10}^{-3}d{m}^3}{22.4d{m}^3}$= Number of moles

$\Rightarrow$ Number of moles= $0.0042$

Number of moles=$\frac{Weight}{Molecularmass}$

$\therefore$ Molecular mass= $\frac{0.2231g}{Numberofmoles}=\frac{0.2231g}{0.0042mole}$

$=53.11g/mole$

$\therefore$ Molecular mass= $53.11g/mol$.