Question

The elevation in boiling point of a sol. Of 0.25m concentration with Kb = 0.052 is ​

Answer 1

Answer:

As we know that, depression in boiling point,

ΔT

b

=k

b

.m

where,

ΔT

b

= Elevation in boiling point = 0.52

k

b

= molal elevation of boiling point = 0.52

m = molality of solution = ?

∴0.52=0.52×m

⇒m=1

As,

m=

Kg of solvent

moles of solute

=1

⇒ As the molality is 1, it signifies that 1 mole of urea is present in 1 kg of water.

∴ no. of moles of water in the solution =

18

1000

=55.55;(∵ 18 is the molar mass of water)

As we know,

mole fraction of solute or solvent in the solution =

total no. of moles of solution

no. of moles of solute or solvent

∴ mole fraction of urea in water =

total no. of moles

no. of moles of urea in the solution

⇒ mole fraction of urea in water =

1+55.55

1

=

56.55

1

=0.0176≈0.018

Hence, the mole fraction of urea in the solution is 0.018.