Which of the following reagents may be used to distinguish between phenol and benzoic acid?

With neutral FeCl3 test, phenol gives a violet color while benzoic acid does not react with it. The violet color is due to the formation of a colored complex between the Fe3+ ion and the phenoxide ion. Benzoic acid, being a carboxylic acid, does not react with neutral FeCl3 in the same way.