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Question

Sucrose is twice as large a molecule as glucose. Does 1 molal aqueous solution of sucrose show more freezing point depression than a 1 molal aqueous solution of glucose? WHY OR WHY NOT?

Answer 1

Step 1:

The molality of sucrose solution is m = 1 molal.

The molality of glucose solution is m = 1 molal.

The sucrose and glucose solutions are decomposed in water.

 for  is 1.86 .

Freezing point is .

Where,

 is the change in temperature.

 is the molality depression constant.

m is the molality .

i  is the von' t Hoff factor.

Answer 2

Contd......

Step 2:

Sucrose :

C₁₂H₂₂O₁₁ --------> 12C + 11H₂O

Here i = 12 for sucrose, ( sucrose completely dissociates into 12 ion).

Freezing point of sucrose solution is .

Freezing point of sucrose .

Glucose :

C₆H₁₂O₆ --------> 6C + 6H₂O

Here i = 6 for sucrose, ( glucose completely dissociates into six ion).

Freezing point of sucrose solution is .

Freezing point of sucrose .

So 1 molal aqueous solution of sucrose show more (Twice) freezing point depression than a 1 molal aqueous solution of glucose.

Solution :

1 molal aqueous solution of sucrose show more (Twice) freezing point depression than a 1 molal aqueous solution of glucose.