Pure benzophenone melts at 48.1 degree C. Your sample of benzophenone began to f

Question

Pure benzophenone melts at 48.1 degree C. Your sample of benzophenone began to freeze at 47.0 degree C. When you repeated this measurement, the sample again began to freeze at 47.0 degree C. Give at least two reasonable explanations for this observation. You tried to read the thermometer when your solution containing the unknown began to freeze but were not certain if the reading was 43.5 degree C or 44.0 degree C so you decided to repeat this by melting the solidifying mass. The new reading you observed was clearly 41.0 degree C. What happened? Clearly explain your reasoning.

Explanation / Answer

Question 3:

Explanation:

Melting point of any pure sample would be equal to freezing point. so, freezing point of pure benzophenone is also 48.1C. Therefore,

1. it may be possible that the sample is not pure. impurities present in benzophenone would always lower its freezing point (depression in freezing point)

2. the sample may still be be pure. But if the mesurement is not done at atmospheric pressure conditions, it may still give different values. decrease in pressure would give decrease in temperature values.

Question 4:

Explanation:

1. the solution could be a mixture with some amount of one of the component may have evaporated when it reached its boiling thereby increasing the concentration of the other component.

2. If one of the component in the mixture has lower freezing than the other, it would start freezing first in such a way that it may limit the movability of the other component but not exactly in the same manner everytime. this may also lead to this obervation

3. conformational changes in structures can also lead to this especially known in proteins.

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