Question

Benzoin and Maleic Acid have the same melting point (136-137 °C). Your TA gave you an unknown compound that has a melting point of 136-137 °C. You added a small amount of pure benzoin to your unknown compound and the melting point of the mixture was 136-137 °C. You added a small amount of maleic acid to your unknown compound and the melting point of the mixture was 124-129 °C. What is the unknown compound likely to be?

Answer 1

The unknown compound is likely benzoin, as its melting point remained unchanged when mixed with pure benzoin, but dropped when mixed with maleic acid.

Step-by-step explanation:

The unknown compound is likely to be benzoin because when combined with pure benzoin, the melting point of the mixture did not change (remained 136-137 °C). This suggests that the unknown compound and benzoin are the same since a mixture of two different compounds typically shows a depressed melting point due to the disruption of the crystal lattice, known as melting point depression. However, when maleic acid was added to the unknown compound, the melting point dropped to 124-129 °C, indicating that the unknown was not maleic acid because the different compounds mixed together led to the expected melting point depression.