What is the molality of a solution of water and kcl if the freezing point of the solution is –3°c? (kf = 1.86°c/m; molar mass of water = 18
g.

Answer : The molality of a solution is, 0.806 mole/Kg

Explanation :

First we have to calculate the Van't Hoff factor (i) for KCl.

The dissociation of will be,

So, Van't Hoff factor = Number of solute particles = = 1 + 1 = 2

Now we have to calculate the molality of solution.

Formula used for lowering in freezing point :

or,

where,

= change in freezing point

= temperature of solution =

= temperature of pure water =

= freezing point constant  =

m = molality  = ?

i = Van't Hoff factor = 2

Now put all the given values in this formula, we get the molality of the solution.

Therefore, the molality of a solution is, 0.806 mole/Kg

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