Question

How will the identification of a component be affected if drying agent was left in the sample?

Answer 1

• Unknown compounds are generally identified by determining their melting points.
• If the compound is not properly dried (i.e. contains drying agent), than it means the compound is impure.
• The presence of drying agent in the compound act as an impurity.
• A pure compound has high molecular symmetry.
• Impurities are tend to defect the crystal lattice of pure compound.
• An impurity is rather assymetrical, or is a poorly organized structure.
• If the impurites (i.e. drying agent) are present, the melting point will deviate because melting point is also dependent on the high symmetry and organization of molecular structures, just as the vapor pressure.
• Foreign substances in a crystalline solid disrupt the repeating pattern of forces that holds the solid together. So a smaller amount of energy is required to melt the part of the solid surrounding the impurity.

           This explains the melting point depression (lowering) observed from impure solids.