Question

What would be the effect of each of the following on the calculated molecular weight of...

What would be the effect of each of the following on the calculated molecular weight of the solute?
A)some cyclohexane evaporated while the freezing point of pure cuclohexane was being measured.
B)some cyclohexane evaporated after the solute was added.
C)a foreign solute was already present in the cyclohexane.
D) the thermometer is not calibrated correctly.it gives a temperature that is 1.5 c too low at all temperatures

Homework Answers

Answer #1

A and B. The solution becomes more concentrated because the volume decreases. The higher concentration will depress the freezing point so it appears as an decrease in molecular weight. It is a decrease because the same mass causes an increased depression.

C. Again, the freezing point will be depressed a bit more due to the contamination and the solute will appear to have a smaller molecular weight.

D. If you don't know the error, the freezing point will appear to be a lower temperature, again resulting in an apparent lower molecular weight.

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