NEET Solved Paper 2014 Question 7
Question: Of the following 0.10 m aqueous solutions, which one will exhibit the largest freezing point depression? [AIPMT 2014]
Options:
A) KCI
B) $ C _6H _{12}O _6 $
C) $ Al _2{{(SO _4)}_3} $
D) $ K _2SO _4 $
Show Answer
Answer:
Correct Answer: C
Solution:
$ \Delta T _{f} $ (freezing point depression) is a colligative property and depends upon the van’t Hoff factor (i)
i.e., number of ions given by the electrolyte in aqueous solution.
$ \Delta T _{f}=i\times K _{f}\times m $ where, $ K _{f} $ = molal freezing point depression constant. m = molality of the solution
$ \therefore $ $ K _{f} $ and m are constant, $ \Delta T _{f}\propto i $
[a] $ KCl(aq){K^{+}}(aq)+C{l^{-}}(aq), $ (Total ions = 2 thus, i = 2)
[b] $ C _6H _{12}O _6no,ions[i=0] $
[c] $ Al _2{{(SO _4)}_3}(aq)2A{l^{3+}}+3SO_4^{2-} $ [Total ions =5, thus, i = 5]
[d] $ K _2SO _4(aq)2{K^{+}}+SO_4^{2-} $ [Total ions = 3, t Thus, i = 3]
Hence, $ Al _2{{(SO _4)}_3} $ will exhibit largest freezing point depression due to the highest value of i.
