Question

Match the following aqueous solutions with the appropriate letter from the column on the right.

1. 0.11 m Fe(NO3)3 A. Lowest freezing point

2. 0.17 m Mn(NO3)2   B. Second lowest freezing point

3. 0.15 m CoBr2   C. Third lowest freezing point

4. 0.49 m Urea(nonelectrolyte) D. Highest freezing point

Answer 1

ΔTf = i*Kf*m

ΔTf is the depression in freezing point

ΔTf will be maximum when i*m is maximum

so,

freezing point will be lowest when i*m is maximum

freezing temperature is maximum when ΔTf will be minimum

i is the number of ions that a compound can break into

1)

1)

Fe(NO3)3

i = 4

Fe(NO3)3 breaks into 1 Fe+ ion and 3 NO3- ions

so,

i*m = 4*0.11 = 0.44

2)

Mn(NO3)2

i = 3

so,

i*m = 3*0.17 = 0.51

3)

Co(Br)2

similarly:

i = 3

i*m = 3*0.15 = 0.45

4)

urea

This is non electrolyte

i = 1

i*m = 0.49

1. matches to D

2. matches to A

3. matches to C

4. matches to B