Given a pure sample that is either pure benzoic acid or 2-naphthol give a procedure that can be used to determine the identity of the sample?

Answer 1

Lets see.

Add neutral ferric chloride to the sample solution. A coloured solution is obtained if it is 2-naphthol (most phenols give colour with neutral ferric chloride solution).

Add sodium bicarbonate to the sample solution. Carboxylic acids evolve carbon dioxide gas. Phenols (except strong ones like picric acid) does not.

Both 2-naphthol and benzoic acid will evolve hydrogen when treated with metallic sodium (test not advisable to do) and NaOH.

Phenols form pleasent smelling esters when treated with carboxylic acids where as benzoic acid will be fruity odour with alcohols or phenols.

Both benzoic acid and 2-naphthol melts about 1220C whereas the boiling point of benzoic acid is 2490C and that of 2-naphthol is 2850C.

Answer 2

One possible procedure is to measure the melting point of the sample. Benzoic acid has a higher melting point (122-123°C) compared to 2-naphthol (120-123°C). By comparing the observed melting point with the reported values, the identity of the sample can be determined. Additionally, performing a solubility test can differentiate these compounds, as benzoic acid is soluble in hot water while 2-naphthol is not.