Question

A sample of `20.0`g of a compound (molecular weight `120`)which is non electrolyte is dissolved in `10.0`grams of ethanol`(C_(2)H_(5)OH)`. If the vapour pressure of pure ethanol at the temperature used is `0.250`atm ,what is the vapour pressure of ethanol above the solution
A. `0.250`atm
B. `0.83`atm
C. `0.125`atm
D. `0.141`atm

Answer 1

Correct Answer - D
`(P^(@)-P_(S))/(P^(@)) =(n)/(n+N)`
`=(0.25-P_(s))/(0.25)=((20)/(120))/((20)/(120)+(10)/(46))=(0.167)/(0.167+0.217)`
`0.25-P_(S)=(0.25xx0.167)/(0.167xx0.217)`
`:.P_(S)=0.141`