How will the purity of the recrystallized product be determined?

The purity of the recrystallized product is determined primarily by measuring its melting point. When a pure substance is heated, it melts at a sharp, specific temperature. However, impurities in the substance disrupt the orderly lattice structure of the solid, leading to a broader melting range and a lower melting point. By carefully measuring the melting point of the recrystallized product and comparing it to the known melting point of the pure compound, one can assess the level of purity present.

Additionally, the presence of impurities often introduces a tail or a slippage in the melting point, which serves as a clear indicator of non-purity. Thus, if the melting point of the recrystallized product is consistent with the expected value for the pure compound, it indicates high purity. If there's a significant deviation, it suggests the presence of impurities affecting the crystalline structure.

In contrast, while methods like refractive index measurement or infrared spectrum analysis can provide information about compound identity and presence of specific functional groups, they do not directly measure the purity with the same reliability as melting point determination. Solubility testing is also useful for assessing the general characteristics of compounds, but it is not a definitive method for purity assessment.