Question

Which pair of aqueous solutions is given in order of increasing freezing point?

(1) 0.010m Na3PO4 < 0.030m NaCl

(2) 0.020m NaI < 0.030m glucose

(3) 0.010m CaCl2 < 0.020m KCl

(4) 0.010m Na3PO4 < 0.020m Na3PO4

(5) 0.020m glucose < 0.010m CaCl2

Answer 1

1) Na₃PO₄ will dissociate into 3Na⁺ & 1 PO₄^3-

So, total molality of Na₃PO₄ will be 4*0.01 = 0.04 m

NaCl will dissociate into 1 Na⁺ & 1 Cl^-

So total molality of NaCl will be 2*0.03 = 0.06 m (correct option)

2) NaI will dissociate into 1 Na⁺ & 1l^-

So total molality of Nal will be 2*0.02 = 0.04 m

Glucose wont dissociate

Hence, (incorrect option)

3) CaCl₂ will dissociate into 1 Ca²⁺ ion & 2 Cl^- ions

Thus, total molality = 0.01*3 = 0.03 m

KCl will dissociate into K⁺ & 1 Cl^- ion

Thus, total molality = 2*0.02 = 0.04

Hence (correct option)

4) Na₃PO₄ will dissociate into 3Na⁺ & 1 PO₄^3-
So, total molality of Na₃PO₄ will be 4*0.01 = 0.04 m

Na₃PO₄ will dissociate into 3Na⁺ & 1 PO₄^3-
So, total molality of Na₃PO₄ will be 4*0.02 = 0.08 m

Hence (correct option)

5) glucose wont dissociate

CaCl₂ will dissociate into 1 Ca²⁺ ion & 2 Cl^- ions

Thus, total molality = 0.01*3 = 0.03 m

Hence (correct option)