The freezing point of diet soda is higher than the freezing point of regular sod

Question

The freezing point of diet soda is higher than the freezing point of regular soda, but lower than 0 degree C, the freezing point of pure water. a) Explain why both diet and regular soda freeze at temperatures lower than 0 degree C. b) Why does diet soda freeze at a higher temperature than regular soda? In order to find the molar mass of an unknown compound, a research scientist prepared a solution of 0.930 g of unknown in 125 g of a solvent. The pure solvent had a freezing point of 74.2 degree C, and the solution had a freezing point of 73.4 degree C. Given the solvent's freezing-point depression constant, K_f = 5.50 degree C/m, find the molar mass of the unknown. The freezing point of a 1 molal aqueous solution of the nonelectrolyte ethylene glycol (the principal constituent of automotive antifreeze) is about -2 degree C. The freezing point of a 1 molal aqueous solution of NaCl, a strong electrolyte, is about -4 degree C. If freezing-point depression is a colligative property, it should depend only on the concentration of dissolved particles. Explain this apparent discrepancy.

Explanation / Answer

Ans 1 . A) The regular soda has some amount of solute along with sugar dissolved in water

The diest soda has the same composition as that of regular soda but except sugar.

Whenever any volatile solute is added into the solvent it decreases its freezing point . This is called as the colligative property of the solution . And this is the reason why normal soda and the diet soda both have freezing points less than 0 degree celsius.

The depression in freezing point is given as ,

Delta Tf = kf . m

where kf is the freezing point constant of solvent

and m is the molality of solution

Ans 1 . B ) The diet soda has same ingredients as that of regular soda but except sugar . So we can say that the regular soda has more amount of solute dissolved into water .

As i mention earlier , that depression in freezing point is directly related to molality ( Delta Tf = kf . m) , so more solute , more molality and hence more depression in freezing point .

Hence the regular soda has a freezing point lower than diet soda.

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