Posted by Marcus on .
Which of the following solutes in aqueous solution would be expected to exhibit the smallest freezingpoint lowering (assuming ideal behavior?
0.1 m NaCl
.2 m CH3COOH
.05 m Al2(SO4)3
.1 m MgCl2
.25 m NH3
What would be the steps to picking the right option? Because just picking .05 because it appears to be the smallest amount is likely wrong.

Chemistry 
DrBob222,
delta T = i*Kf*m
Since Kf is constant we can forget that. dT depends upon i and m so
i*m for each.
NaCl is 0.1*2 = ? for i = 2
CH3COOH is 0.2*1 for i = 1
Al2(SO4)3 is 0.05*5 for i = 5
MgCl2 i = 3
NH3 i = 1
The greatest i*m causes the greatest dT (or the smallest i*m causes the least dT). 
Chemistry 
Jes,
D