Impure sample of Naphthalene can be purified by Sublimation.

Sublimation is a process of changing solid to gas and vice-versa. And when naphthalene changes into gas then impure substance would be left.

Purification of Impure Sample of Naphthalene

Naphthalene is a white crystalline solid that is commonly used as a moth repellent and in the production of dyes and plastics. When naphthalene is obtained from natural sources or synthesized, it may contain impurities that can affect its purity and quality. To obtain a pure sample of naphthalene, various purification techniques can be employed. One of the most effective methods for purifying impure naphthalene is through the process of sublimation.

Sublimation:
Sublimation is the process of converting a solid directly into a gas without passing through the liquid phase. In the case of naphthalene, impurities present in the solid sample have different sublimation temperatures compared to naphthalene. When the impure sample of naphthalene is heated under controlled conditions, naphthalene molecules sublime and rise to the top of the container, while the impurities remain behind.

Procedure:
The following steps can be followed to purify an impure sample of naphthalene through sublimation:

1. Obtain the impure sample of naphthalene.
2. Place the impure sample in a sublimation apparatus, which typically consists of a glass container with a stopper and a delivery tube.
3. Heat the impure sample gently using a Bunsen burner or a heating mantle. The temperature should be below the melting point of naphthalene but high enough to facilitate sublimation.
4. As the impure naphthalene sample is heated, naphthalene molecules will sublimate and rise as a vapor. The vapor will then cool and condense on the upper walls of the container or the stopper.
5. The condensed pure naphthalene can be collected by scraping it off the walls of the container or the stopper.
6. The remaining impurities can be discarded.

Advantages of Sublimation:
- Sublimation is a relatively simple and cost-effective method for purifying solid substances.
- It allows for the separation of substances with different sublimation temperatures, making it highly selective.
- It does not require the use of additional solvents or chemicals, minimizing the risk of contamination.
- Sublimation can be carried out on a small scale in a laboratory or on a larger scale in an industrial setting.

In conclusion, the purification of impure naphthalene can be effectively achieved through the process of sublimation. This method allows for the separation of naphthalene from impurities based on their different sublimation temperatures, resulting in a pure sample of naphthalene.