1.

0.15 molalsolutionof NaCIhas freezingpoint -0.52 ^(@)C Calculatevan'tHofffactor.(K_(f)= 1.86 K kg mol^(-1) )

Answer»


SOLUTION :Given :concentration`= m=0.15 M `
Freezingpoint of THESOLUTION=- 0.52 `.^(@)C`
`K_(f)= 1.86K kg MOL^(-1)`
`:. T_(f) =273 + (-0.52)= 272 .48 K`
`T_(o)= 273 K`
`:.` Depressionin freezingpoint `=DeltaT_(f(OBS))=T_(o) -T_(f)`
`=273- 272.48`
`= 0.52K`
Theoreticaldepression infreezingpoint `= Delta T_(f_(th))`
`Delta _(f_(th)) = K_(f)xx m =1.86 xx 0.15 = 0. 279 K`
van't Hofffactori is
`i= (Delta _(f(ob)))/(Delta_(T_(f_((th)))))=(0.52)/(0.279) = 1.864`


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