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

3) a) This observation is because of having impurities in the sample. It leads to the depression in freezing point.

b) The second possible reason is the solvent effects. If solvent is polar the interactions between solute and solvent will be less hence it can solidify easily.

4) Melting point determination mainly depends on the interactions as well as in the procedure. In the first method student not cleaned the apparatus properly. It creates unexpected interactions between the solute and solvent. Therefore the M.P is varied from exp:1 to exp:2.

The second possible reason is temperature conditions.

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