Which of the following liquids will have the lowest freezing point? A)pureH2O B)aqueous FeI3 (0.030 m) C) aqueous CoI2(0.030 m) D)aqueous NaI (0.030 m) E) aqueous glucose (0.050 m) Solution Pure water will not have depression in freezing point. Hence its freezing point will be highest. Lets compare other 4. ?Tf = i*Kf*m ?Tf is the depression in freezing point ?Tf will be maximum when i*m is maximum so, lowest freezing point is for that solution which has higher value of i*m FeI3 dissociates into 1 Fe3+ and 3 I- So, i = 4 Hence, i*m = 4*0.03 = 0.12 CoI2 dissociates into 1 Co2+ and 2 I- So, i = 3 Hence, i*m = 3*0.03 = 0.09 NaI dissociates into 1 Na+ and 1 I- So, i = 2 Hence, i*m = 2*0.03 = 0.06 glucose is non electrolyte and hence it will not dissociate So, i = 1 Hence, i*m = 1*0.05 = 0.05 Increasing order of i*m is: glucose NaI CoI2 FeI3 This will be the order of decreasing freezing point So, compounds from higher to lower freezing point are: glucose NaI CoI2 FeI3 FeI3 has least freezing point Answer: B .

1. Which of the following liquids will have the lowest freezing point?
A)pureH2O
B)aqueous FeI3 (0.030 m)
C) aqueous CoI2(0.030 m)
D)aqueous NaI (0.030 m)
E) aqueous glucose (0.050 m)
Solution
Pure water will not have depression in freezing point. Hence its freezing point will be highest.
Lets compare other 4.
?Tf = i*Kf*m
?Tf is the depression in freezing point
?Tf will be maximum when i*m is maximum
so, lowest freezing point is for that solution which has higher value of i*m
FeI3 dissociates into 1 Fe3+ and 3 I-
So, i = 4
Hence, i*m = 4*0.03 = 0.12
CoI2 dissociates into 1 Co2+ and 2 I-
So, i = 3

2. Hence, i*m = 3*0.03 = 0.09
NaI dissociates into 1 Na+ and 1 I-
So, i = 2
Hence, i*m = 2*0.03 = 0.06
glucose is non electrolyte and hence it will not dissociate
So, i = 1
Hence, i*m = 1*0.05 = 0.05
Increasing order of i*m is:
glucose
NaI
CoI2
FeI3
This will be the order of decreasing freezing point
So, compounds from higher to lower freezing point are:
glucose
NaI
CoI2
FeI3
FeI3 has least freezing point
Answer: B