The normal freezing point of a certain liquid

x

is

0.4°c

, but when

5.90g

of urea

nh22co

are dissolved in

450.g

of

x

, it is found that the solution freezes at

−0.5°c

instead. use this information to calculate the molal freezing point depression constant

kf

of

x

Answer : The molal freezing point depression constant of X is

Explanation :  Given,

Mass of urea (solute) = 5.90 g

Mass of X liquid (solvent) = 450.0 g

Molar mass of urea = 60 g/mole

Formula used :  

where,

= change in freezing point

= freezing point of solution =

= freezing point of liquid X=

i = Van't Hoff factor = 1  (for non-electrolyte)

= molal freezing point depression constant of X = ?

m = molality

Now put all the given values in this formula, we get

Therefore, the molal freezing point depression constant of X is

water and alcohols have similar properties because water molecules contain hydroxyl groups that can form hydrogen bonds with other water molecules and with alcohol molecules, and likewise alcohol molecules can form hydrogen bonds with other alcohol molecules as well as with water.