AP EAMCET Engineering 2018 Apr 24 Shift 1 Paper

First, we will calculate molarity as follows:
Molarity (C)=

Mass‌of‌solute

Molar‌mass‌of‌solute×Mass‌of‌solvent

×1000
=

12.25×1000

122.5×250

=0.40
Now, the degree of ionization is calculated as:
α=√

Ka

C

=√

1.44×10−3

0.4

=0.66
Now, Van’t Hoff factor (i) is calculated as:
Total number of moles is equal to 1−α+α+α=1+α
i=

Moles‌after‌dissociation

Moles‌before‌dissociation

=1+α1
=1+α
Since, value of α is 0.06
Therefore,
i=1+0.06
=1.06
The change in freezing point is calculated as follows:
ΔTf=iKfm
=1.06×0.4×1.86
=0.789°C