Question

Which of the following solutions will have the lowest freezing point? A) 0.010 m K Br B) 0.010 m Na2CO3 C) 0.035 m C6H12O6 D) 0.015 m BaCl2

Answer 1

more concentrated soution gives more molality. Hence on these grounds, C6H12O6 is expected to have lowest freezing point. But

depression in freezign point = kf*m*i where i is van't Hoff factor and for glucose it is 1. So on these grounds it is ruled out for producing lowest freezing point. Second next concentration is 0.015 BaCl2. its i value is 3. 0.015*0.3= 0.45 which is more than 0.35*1 for sugar. Hence it produces lowest freezing point. Na2CO3 moality is less than that of BaCl2 even though its van't hoff factor is same as that of BaCl2.