In the determination of a melting point, why is it necessary to: a. Use a powder

Question

In the determination of a melting point, why is it necessary to: a. Use a powdered rather than a crystalline sample? b. Use a new capillary tube for each determination? c. Not heat the sample too rapidly near the melting point? A certain substance, melting at 188-189 degree C, is suspected to be 4-aminobenzoic acid. How could you be reasonably certain that the substance is actually 4-aminobenzoic acid and not another compound with the same melting point? Which has a lower freezing point: ice of ice cream? Why?

Explanation / Answer

Answer 1 : Use a powder than a crystalline materials since it will be homogenous.

Answer 2: Acylation of amino group is necessary here and then determine the melting point of derivative which will finally confirm that given compound is 4-Aminobenzoic acid.

Answer 3: Ice of ice cream have lower melting point than ice cream because addition of foreign substances in ice    will leads to depression in freezing point.

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