Question

What is the correct sequence of the increasing order of freezing points at one atmosphere of the following $1.0M$ aqueous solution?
$1.$ Urea, $2.$ Sodium chloride, $3.$ Sodium sulphate, $4.$ Sodium phosphate.
Select the correct answer using the codes given below

• A. 4, 3, 1, 2
• B. 3, 4, 2, 1
• C. 3, 4, 1, 2
• D. 4, 3, 2, 1

Answer 1

Answer: (D)

vant Hoff factors for urea, $NaCl,N{a}_{2}S{O}_4$ and $N{a}_{3}P{O}_4$ are $1,2,3$ and $4$ respectively.
As $\Delta T_f\propto im$ , so $\Delta T_f$ for urea, $NaCl$, $N{a}_{2}S{O}_4$ and $N{a}_{3}P{O}_4$ are proportional to $1,2,3$ and $4$ respectively. Hence, freezing point order is $N{a}_{3}P{O}_4<N{a}_{2}S{O}_4<NaCl<$ Urea