Question

Benzene and toluene form ideal solution over the entire range of composition. The vapour pressure of pure benzene and naphthalene at `300K` are `50.71 mm Hg` and `32.06mm Hg`, respectively. Calculate the mole fraction of benzene in vapour phase if `80g` of benzene is mixed with `100g` of naphthalene.

Answer 1

Molar mass of `C_(6)H_(6)=78" g "mol^(-1)`
Molar mass of `C_(6)H_(5)CH_(3)=92" "gmol^(-1)`
No. of moles of `C_(6)H_(6)=(80)/(78)=1*026`mole
no. of moles of `C_(6)H_(5)CH_(3)=(100)/(92)=1*087` mole
Mole fraction of `C_(6)H_(6)`
`x_(B)=(1*026)/(1*026+1*087)=0*486`.