1.

The vapour pressure of ethanol and methanol are `44.0 mm Hg` and `88.0 mm Hg`, respectively. An ideal solution is formed at the same temperature by mixing `60 g` of ethanol with `40g` of methanol. Calculate the total vapour pressure of the solution and the mole fraction of methanol in the vapour.A. `0.66`B. `0.55`C. `0.11`D. `0.33`

Answer» Correct Answer - A
Mole of `CH_(3)CH=(40)/(32)=1.25`
Mole of `CH_(3)CH_(2)OH=(60)/(46)=1.304`
Let `CH_(3)CHrarrA,C_(2)H_(5)OHrarrB`
`X_(A)=(n_(A))/(n_(A)+n_(B))=(1.25)/(1.25+1.304)=0.49`
`:.X_(B)=0.51`
`:.P_(T)=P_(A)^(@)X_(A)+P_(B)^(@)X_(B)=88.7xx0.49+44.5xx0.51`
`:.P_(T)=43.480+2.695=66.175`
`P_(A)=43.8 , :. X_(A)=(P_(A))/(P_(T))=(43.48)/(66.175)=0.66`


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