Question

a good sample of benzoic acid melts at 121-122. however, a student had a sample of benzoic acid that melted over a range, 105-115. what could the student concllude about his sample?

Answer 1

Answer:

The student conclude that the sample of benzoic acid is impure.

Explanation:

The observed melting point of benzoic acid when a student melts his/her sample is low than the actual value. The reason for this might be:

(a) The most probable reason is that the sample is impure. Impurities in the sample leads to lowering the value of the melting point. The reason for the phenomenon is that when impurity is present in the compound, the pattern of the crystal lattice disturbs and thus it less amount of heat is require to break the lattice.

(b) There may be some experimental errors like:

1. Non-uniform heating of the sample
2. The sample is not tightly filled in the capillary if the student is    following Kjeldahl's flask method.
3. If the student is using melting point machine, there there might be some instrumental errors.

The student conclude that the sample is impure.