1.

A certain substance `A` tetramerizes in water to the extent of `80%`. A solution of `2.5 g` of `A` in `100 g` of water lowers the freezing point by `0.3^(@)C`. The molar mass of `A` is a.`120` , b.`61` ,c.`60` ,d.`62`A. `122`B. `31`C. `244`D. `62`

Answer» Correct Answer - D
`alpha =(1-i)/(1-(1)/(n))`
`(1-i)/(1-(1)/(4)) ,i=0.4`
`DeltaT=iK_(f)xxm`
`0.3=0.4xx1.86xx(w_(b)xx1000)/(m_(B)xxw_(A))`
`0.3=0.4xx1.86xx(2.5xx1000)/(m_(B)xxw_(A))`
`m_(B)=62`


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