Question

A solution of `0.450` g of urea (mol wt. `60`)in `22.5g`of water showed `0.170^(@)C` of elecation in boiling point. Calculate the molal elevation constant of water
A. `0.17^(@)C`
B. `0.45^(@)C`
C. `0.51^(@)C`
D. `0.30^(@)C`

Answer 1

Correct Answer - C
`{:("Wt. of solute",w=0.450g),("Wt. of solvent",W=22.5g ),("Mol. of solute",m=60),("molal elevent constant",K_(b)=?),("Boiling point of elevation",DeltaT_(b)=0.170^(@)C):}`
Substituting these values in the equation
`K_(b)=(mxxWxxDeltaT_(b))/(1000xxw)=(60xx22.5xx0.170)/(1000xx0.450)=0.51^(@)C`