Question

out of 1M urea solution and 1M KCl solution,which one higher freezing point?

Answer 1

In this case molarity is same therefore vant hoff factor is deciding factor .
Vant hoff factor for -
KCl - 2
Urea -1
So KCl will have highest freezing

Answer 2

Answer: 1M urea solution has higher freezing point.

Explanation:

Depression in freezing point is given by:

$\Delta T_f=i\times K_f\times m$

$\Delta T_f=T_f-T_f^0$ = Depression in freezing point

i= vant hoff factor

$K_f$ = freezing point constant

1. For 1 M urea

i= 1 as it is a non electrolyte and does not dissociate.

2. For 1 M $KCl$

i= 2 as it is a electrolyte and dissociate to give 2 ions.

$KCl\rightarrow K^{+}+Cl^{-}$  

Thus as vant hoff factor is higher for $KCl$, thus depression in freezing point will be higher.

Thus 1M urea solution has higher freezing point.