Question

What is the purification method used for an impure sample of Naphthalene?

Answer 1

Crystallization:

• Crystallization is the process of separating solid compounds from the solution in the form of crystals.
• This method is mainly employed for the separation of a solid from the solution.
• It is a physical change.

Purification of impure napthalene:

• To obtain pure naphthalene, generally, the process of crystallization is used.
• Though it requires a lot of energy, resulting in higher costs.
• Hence, the use of solvents can serve the purpose of the purification of naphthalene.
• One such solvent is phosphoric acid because it does not react with impure naphthalene.
• Mixing the impure naphthalene with the solvent in the ratio of $1.5:1$ at a temperature reaching ${80}^{\mathrm{o}}\mathrm{C}$.
• After cooling the mixture to room temperature, a solid white residue of pure naphthalene and a yellowish liquid containing the solvent and impurities remained.
• Finally, the pure naphthalene was separated from the solvent through filtration and washed with distilled water.