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When dissolved in benzene, a compound C(...

When dissolved in benzene, a compound `C_(38)H_(30)` partilly dissociates by the following equation:

`25.6 g` of `C_(38)H_(30)` is dissolved in `400 g` of benzene, the freezing point is lowered by `0.680^(@)C`. What percentage of `C_(38)H_(30)` molecules have dissociated? `(K_(f)=4.9)`

Text Solution

Verified by Experts

`DeltaT_(f)=iK_(f)m`
`i=(DeltaT_(f))/(K_(f)(((W_(B))/(Mw_(B)))/W_(A)xx1000))=i=(0.68)/(4.9(((25.6)/(486))/400xx1000))`=1.0538`
Consider
Total moles=`1-x+2x=1+x`
`i="Total moles"/"Initial moles"=(1+x)/1`
`rArr 1.0538 =(1+x)/1 rArr x=0.0538%`
`rArr` Percentage dissociation = 5.38%
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