Question

A gas mixture is made by combining 7.0 g each of Ar, Ne, and an unknown diatomic gas. At STP, the mixture occupies a volume of 16.60 L. What is the molar mass of the unknown gas?

Answer 1

Considering molar mass of

`Ar->40" g/mol"`

`Ne->20" g/mol"`

`"Molar mass of unknown gas"->m" g/mol"`

The total number of moles Ar , Ne and unknown gas in the gas mixture each having mass of 7g is

`=(7/40+7/20+7/m)mol`

Total Volume of these three gases at STP is

`(7/40+7/20+7/m)molxx22.4L/"mol"=16.60L`

`=>(7/40+7/20)22.4L+7/mxx22.4L=16.60L`

`=>21/40xx22.4+7/mxx22.4=16.60`

`=>11.76+7/mxx22.4=16.60`

`=>7/mxx22.4=(16.60-11.76)=4.24`

`=>m=(7xx22.4)/4.24~~36.98"g/mol"`