Question

A solution of 1.25g of a certain non-volatile substance in 20g of water freezes at 271.94K. Calculate the molecular mass of the solute `(K_(f)=1.86" K kg mol"^(-1))`.
A. `179.97 g "mol"^(-1)`
B. `207.8 g "mol"^(-1)`
C. `209.6 g "mol"^(-1)`
D. `109.6 g "mol"^(-1)`

Answer 1

Correct Answer - D
`M_(2) = (K_(f) W_(2) xx 1000)/(Delta T_(f) W_(1))=(1.86 xx 1.25 xx 1000)/((273-271.94) xx20)=109.6`