How would the molar mass determination of a strong electrolyte ionic compound by

Question

How would the molar mass determination of a strong electrolyte ionic compound by the following scenarios?

A. The researcher assumed that alpha=1 at concentration 0.1m.

B. The cooling curve for the solvent was analyzed correctly, but the minimum temperature of the supercooled region of the cooling curve was used to determine the freezing point of the solution.

C. The thermometer was incorrectly calibrated and consistently showed a temperature 0.08 degrees C higher than the actual temperature for all measurements

D. A sample of potassium chloride is contaminated with a small amount of sodium bromide. (Assume that the measurements were taken under conditions where alpha=1 for both compounds) E. The distilled water used in the experiments was contaminated with a very low concentration of magnesium chloride.

Explanation / Answer

Molar mass by freezing point depression

A. Molar mass is inverse of moles, so with alpha = 1, 0.1 m solution

moles = 0.1

molar mass = grams of solute/0.1 m

B. If the freezing point is determined from supercooled region, the freezing point would be lower and thus molar mass would also be lower

C. If thermomemter showed higher temperature, molar mass would be higher.

D. For a contaminated solution, molar mass of solute would be lower as amount of solute would be less in solution

E. Of distilled water used is contaminated the resulting molar mass would lower than actual value

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