Question

Assuming that the following salt solution have effective ion concentration equal to the actual salt concentration determine the approximate freezing point of the solution: 

 A 0.1 F potassium sulfate solution.

Answer 1

$\Delta T_f=i×m×K_f...... (i)$

where $\Delta T_f$  is the freezing point depression,i is the vanhoff's factor, m is the molality of the solute and $K_f$  is the freezing point depression constant

here value of K_f for water is 1.86 , m is 0.1

now calculating value of $i$

As potassium sulfate solution will undergo 100 % dissociation

So the total 3 ions are formed on 100% dissociation so value of $i$ =3

Substituting these values in the equation (1) we get $\Delta T_f=3×0.1×1.86=0.558°C$

Freezing point =$T_f-\Delta T_f =(0-0.558) °C$

$=-0.558°C$