Benzoic acid and 2-naphthol have the same melting point (121 - 122 °C). An unknown compound has a melting point of 121 - 122 °C. Melting point of a mixture of pure benzoic acid and your unknown sample was 116-122 °C. Melting point of a mixture of 2-naphthol and your unknown sample was 110 - 116 °C. What is your unknown?