Heptane and octane form an ideal solution. At `373 K`, the vapour pressure of the two liquids are `105.0` kPa and `46.0` kPa, respectively. What will be the vapour pressure, of the mixture of `25 g` of heptane and `35 g ` of octane ?

Explanation

Mw of heptane, `C_(7) H_(16)`, `Mw_(A) = 100`
Mw of octane, `C_(8) H_(18)`, `Mw_(B) = 114`
`n_(A)=W_(A)/(Mw_(A))=25/100=0.25` , `n_(B)=35/114=0.3`
`chi_(A) = (0.25)/(0.25 + 0.30)` , `chi_(B) =(0.3)/(0.25 + 0.30)`
`= 0.45` `= 0.55`
`p=p_(A)^@chi_(A) + p_(B)^@chi_(B)`
`105.0 xx 0.45 + 46.0 xx 0.55`
`= 47.25+25.30`
`= 72.55` kPa