Question

1. Why do soluble impurities affect the melting point while insoluble impurities are expected not to affect the melting point? (3 points) 2. Why cold solvents are preferred during recrystallization and when is recrystallization selected vs other purification techniques you have learned during 3210 labs. (3 points) 3. The solid compound "X" has two components (A and B). After heating the solid powder (X), one component (A) is left and the other component (B) evaporated directly. Comment on the nature of A and B and name the process of phase change that resulted in evaporation of B (3 points).

Answer 1

Salution 1 vious intermolecular 0 1 STARTED Most of the compounds we deal with in the laboratory are crystalline and these compounds have molecules arranged in a regular, lightly packed repeating crystal lattice. Lattice is held together by various unte forces. Note » Higher the forces holding the solid together, the higher is its melting point Soluble impurities in crystalline solids disubt the repeating pattern of forces. So a small amount of energy is required to meet the solid. Dere tee which melting point of a substance decreases as compared to its pure state when ceimpurity is soluble. It melts over a wide range of tempe -rature Insoluble impurities Insoluble impurities have no effect on meltino boint of a substance because these impurities donot disrupt the pattern of forces. This donot affect the melting paint.