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Assming complete dissociation, Calculate...

Assming complete dissociation, Calculate the expected the expected freezing point of a solution prepared by dissolving 6.0 g of Glauber's salt. `Na_(2)SO_(4). 10H_(2)O` in 0.1 kg of water. (Given value of `K_(f)=1.86 K kg mol^(-1))`.

Text Solution

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`N_(2)SO_(4).10H_(2)O` dissociates in aqueous solution as:
`N_(2)SO_(4).10H_(2)Oto2N_(a)^(+)+SO_(4)^(2-)+(10H_(2)O)`
`"Van't Hoff factor "(i)=("No.of particles after dissociation")/("No. of particles origibally present")=(2+1)/1=3`
`(10H_(2)O "moleculess are nbot considered as these are the part of the solvent")`
`DeltaT_(f)=ixxK_(f)xm=ixxK_(f)xxW_(B)/(M_(B)xxW_(A))`
` i=3, W_(B)=6.0g, W_(A)=0.1 kg, K_(f)=1.86 K kg mol^(-1)`
`M_(B)(Na_(2)SO_(4).10H_(2)O)=(2xx23)+32+(4xx16)+(10xx18)=322g mol^(-1)`
`DeltaT_(f)=(3xx(1.86K kg mol^(-1))xx(6g))/((322 g mol^(-1))xx(0.1 kg))\=1.04 K`
Freezing point of solution `(T_(f))=T_(f)^(@)-DeltaT_(f)=273 K -1.04 K=271.96 K`
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