An unkown compound y is one of the compounds in the list below.

oxalic acid 101 c, benzoic acid 121 c, phenyl succinate 121 c, m- aminophenol 122

a mixture of y and benzoic acid has a melting point of 94 degrees c.
a mixture of y with phenyl succinate has a melting point of 106 degrees c.
a mixture of y with m-aminophenol has a melting point of 102 degrees c.
what is the identity of compound y? explain your reasoning.

Oxalic Acid

Explanation:

This can be actually pretty logic to do.

First, let's remember the principle of mixed melting point.

Usually a melting point of any compound when it's pure, it has a range of 2 °C as much, when it's not pure, the melting point is lower than usual for a range greater than 20 °C. So, When we don't know the compound we are treating, but we have suspects of which could be, we do a mixed melting point. This consists in mixing a portion of the unknown compound with a known compound of a known melting point. If the mix melts at the melting point of the known compound, we can have a hint and reliable source to the identity of the compound.

With this in mind, let's see the mixture of Y with the known compound.

All of the mixes have a melting point lower than all the compounds per separate, so let's analyze every mix to get to the real compound.

Y + benzoic acid = 94°C. In this mixture, if Y were benzoic acid, the melting point should be around 119 - 123 °C, and it's not, because mp decay a lot. We can discart that could be benzoic acid.

Y + phenyl succinate = 106 °C. We already know it's not benzoic acid, and in this case occurs the same as before. Mp was lower than mp of the pheny succinate, and it should be around 119 - 123 °C to get the hint that can be this one. So pheny succinate it's not either.

Y + m-aminophenol = 102 °C. Once again, mp was very low compared to the mp of the aminophenol. If they were the same, mp should be really close to the mp of the m-aminophenol and it's not the case.

The reason of the lowering it's because Oxalic acid has the lower mp of all of them, and it's a different structure from the other that are aromatic rings, so mp decays.

Therefore, the compound here is Oxalic acid