Question

Calculate the amount of ice that will separate out on cooling containing `50 g `of ethylene glycol in `200 g` of water to `-9.3^(@)C (K_(f)` for water =`1.86 K mol^(-1) kg`)

Answer 1

Here mass of solute=`50 g`
`DeltaT_(f)=9.9_(@)`,`K_(f)=1.86 K m^(-1) kg`
Molecular mass of solute `(CH_(2)OH)_(2)`,`Mw_(2)=62`
We have to calculate the mass of water in which the given massof solute will dissolve. The rest of water will freeze out as ice. Applying the relation
`Mw_(2)=(1000.K_(f)W_(2))/(W_(1).DeltaT_(f))`
`w_(1)=(1000.K_(f)W_(2))/(Mw_(2).DeltaT_(f)) =(1000xx1.86xx50)/(62xx9.3)=161.3 g`
Ice that will separate out =`200-161.3 =38.7 g`.