1.

The vapour pressure of pure water at 25^(@)C is 23.62 mm. What will be the vapour pressure of a solution of 1.5 g of urea in 50 g of water ?

Answer»


Solution :According to Raoult's law,
`(P_(A)^(@)-P_(S))/P_(S)=x_(B)=n_(B)/n_(A)=(W_(B)//M_(B))/(W_(A)//M_(A))= `
`P_(A)^(@)=23.62 mm, W_(B)=1.5g, M_(B)=60"mol"^(-1),W_(A)=50 G,M_(A)=18" g mol"^(-1)`
`(23.62-P_(S))/P_(S)=((1.5g)//(60"g mol"^(-1)))/((50g)//(18" g mol"^(-1)))=0.009, 23.63 -P_(S)=0.009 P_(S)`
or `1.009 P_(S)=23.62 or P_(S)=(23.62)/(1.009)=23.41 mm.`


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