Question

At equal concentrations, would a nonelectrolyte (e.g. glucose) or electrolyte (e.g.NaCl) containing solution have a lower freezing point? Why?

Answer 1

Answer:

Solution with electrolyte will have a lower freezing point than the solution with non electrolyte.

Explanation:

Depression in freezing point is given by :

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

Where :

i = van't Hoff factor

$k_f$ = Molal depression constant of solvent

m = molaity of the solution

Let the molality of the glucose and NaCl solution be = m

Molal depression constant of water = $k_f$

1) The values of van't Hoff factor for glucose is = 1 (non electrolyte)

Depression in freezing point of glucose solution :

$\Delta T_f=1\times k_b\time m$

2) The values of van't Hoff factor for NaCl is = 2 (electrolyte)

$NaCl\rightarrow Na^++Cl^-$

Depression in freezing point of NaCl solution :

$\Delta T_f'=2\times k_b\time m$

$\Delta T_f$

$1\times k_b\time m$

1 < 2

Higher the depression in freezing point more will be the lower freezing point of the solution.This means that solution with electrolyte will have a lower freezing point than the solution with non electrolyte.