1.

In a 0.2 molal aqueous solution of aweal acid, HX, the degree of dissociation is 0.3 . Taking K_(f) for water as 1.85, the freezing point of the solution will be nearest to

Answer»

`-0.360^(@)C`
`-0.206^(@)C`
`+0.480^(@)C`
`-0.480^(@)C`

Solution :The weak ACID ionizes as
`{:(,HX,hArr,H^(+),+,X^(-)),("INITIAL",1,,0,,0),("After dissociation",1-0.3,,0.3,,0.3):}`
TOTAL MOLES `=1-0.3+0.3+0.3=1.3`
`i=(1.3)/(1)=1.3`
`DeltaT_(f)=iK_(f)xxm=1.3xx1.85xx0.2=0.481`
`T_(f)=0-0.481= -0.481^(@)C`.


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