Question

An aqueus soution of an organic compound containing 0.6 of it dissolved in 21.7 g of water, freezes at 272.187 K. If the value of `K_(f) is 1.86 K mol^(-1)` for water which freezes at 273 K, calculate the molecular mass of organic compund.

Answer 1

`M_(B)-(K_(f)xxW_(B))/(DeltaT_(f)xxW_(A))`
Mass of compound`(W_(B))=0.6 g`
Mass of water `(W_(A))=21.7 g= 0.0 217 kg`
`(DeltaT_(f))=(273-272.187)=0.813 K`
Molal depression constant `(K_(f))=1.86 K kg mol^(-1))` ltbtgt `M_(B)=((1.86 K kg mol^(-1))xx(0.6 g))/((0.813 K)xx(0.0217 kg))=63.26 g mol^(-1)`