A student followed our lab procedure for this experiment. He started the experim
ID: 1021426 • Letter: A
Question
A student followed our lab procedure for this experiment. He started the experiment by measuring the mass and freezing point of the pure solvent with little error. INstead of quickly finishing the experiement, he went to lunch. After returning he noted that the solvent had absorbed some impurities from the atmosphere. He went ahead and did the experiment anyway. Determine whether the measured freezing point depression in the experiement would increase, decrease, or not change compared to if the solvent has no impurities in it. Also determine whether the measured molality of the solution and the molar mass of the solute would increase, decrease, or not change.
Explanation / Answer
The impurities from the atmosphere increases the amount of matter (colligative particles) inside the solvent. Hence the oserved colligative property of the solvent increases. Hence the measured freezing point depression in the experiement would decrease and the solution will freeze at a very lower temperature. (answer)
The measured molality of the solution increases due to addition impurities. (answer)
molality, m = moles of solute / mass of solvent
=> m = (mass of solute) / [molar mass of solute x mass of solvent]
Since molality is inversely proportional to molar mass, the molar mass of the solute will decrease. (answer)
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