1.

The vapour pressure of a solution of a non-volatile electrolyte (A) in solvent (B) is 95% of the vapour pressure of the solvent at the same temperature. If molarmass of B is 30% of molar mass of A, the same ratio of the solvent and solute are

Answer»

0.15
0.2
`4.0`
5.7

Solution :`p_(s)=95%" of "p^(@), i.e., p_(s)=0.95p^(@)`
`M_(B)=30%" of "M_(A), i.e., M_(B)=0.30M_(A)`
(B = solvent, A = electrolyte)
APPLYING COMPLETE formula
`(p^(@)-p_(s))/(p_(s))=(n_(2))/(n_(1))=(w_(2)//M_(2))/(w_(1)//M_(1))=(w_(2))/(w_(1))XX(M_(1))/(M_(2))=(w_(A))/(w_(B))xx(M_(B))/(M_(A))`
`(p^(@)-0.95p^(@))/(0.95p^(@))=(w_(A))/(w_(B))xx0.30 or (0.05)/(0.95)=(w_(A))/(w_(B))xx0.30`
`"or"(w_(B))/(w_(A))=(0.30xx0.95)/(0.05)=5.7`


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