1.

A solution containing 0.85g of ZnCl_(2) in 125.0 g of watcr freezcs at -0.23^(@)C. The apparent degree of dissociation of the salt is (K _(f) for water = 1.86 k kg mol ^(-1), atomic mas: Zn =65.3 and Cl =35.5)

Answer»

`1.36%`
`73.5%`
`7.35%`
`2.47%`

Solution :MOL wt. `= (k _(F) xx w xx 1000)/( Delta T _(f) xx W)`
`= (1.86xx0.85 xx1000)/( 0.23xx125)~~55 gm`
where
`w= 0.85g`
`W= 125g`
`Delta T_(f) =0^(@)C-(-23^(@)C)=23^(@)C`
Now, `i= (M_("normal"))/(M_("obscrved")) = (136.3)/(55) =2.47`
{:(Zn Cl_(2), HARR, Zn^(++), +, 2Cl^(-)), (1-alpha,, alpha,, 2 alpha):}`
Van't Hoff FACTOR (i)
`= (1- alpha _(eta) + alpha _(eta) +2 alpha_(eta))/(1) =2.47`
`therefore alpha eta = 0.735 = 73.5%`


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