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How many moles of sucrose should be diss...

How many moles of sucrose should be dissolved in 500 g of water so as to get a solution which has a difference of `103.57^(@)C` between boiling point and freezing point :-
`(K_(f)=1.86" K kg mol"^(-1), K_(b)="0.52 K kg mol"^(-1))`

A

`0.5` moles

B

`0.9` moles

C

`0.75` moles

D

`0.65` moles

Text Solution

Verified by Experts

The correct Answer is:
C
`because" "T_(b)=T_(b)^(@)=K_(b)xxm" …(i)"`
`" "T_(f)^(@)-T_(f)=K_(f)xxm" …(ii)"`
`"(i) equation "+" (ii) equation"`
`(T_(b)-T_(f))+(T_(f)^(@)-T_(b)^(@))=m(K_(b)-K_(f))`
`103.57-100=m(1.86+0.52)`
`(3.57)/(2.38)=(n)/(500)xx1000`
`0.75" moles"`
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