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

it means there are 3 atoms of oxygen