Sublimation of Naphthalene

A mixture of impure naphthalene and sand is heated to demonstrate sublimation. Naphthalene sublimes directly from solid to vapor and recrystallizes on a cooled surface, separating it from the non-sublimable impurity.

1. Place about 1 g of impure naphthalene mixed with sand into a 200 ml beaker.
2. Cover the beaker with a round-bottomed flask filled with cold water or ice.
3. Heat the beaker gently on a hotplate or with a low flame.
4. Observe naphthalene vapors rising and depositing as pure crystals on the cold flask and beaker walls.
5. Scrape off the deposited naphthalene crystals.
6. Collect the purified sample in a small flask, weigh it, and determine its melting point to confirm purity.

Sublimation of Mothballs - Science Made Easy:

Separate Naphthalene from the given mixture of sand and naphthalene - Chemistry Plus:

📄 Sublimation - uomustansiriyah.edu.iq: https://uomustansiriyah.edu.iq/media/lectures/6/6_2021_07_16!08_20_55_PM.pdf

• Try using a condenser tube cooled with running water instead of an ice-filled flask.
• Compare sublimation with simple filtration to highlight differences in purification techniques.

• Wear safety goggles, gloves, and a lab coat.
• Naphthalene is toxic if inhaled or ingested; avoid breathing vapors.
• Perform the experiment in a well-ventilated area or fume hood.
• Handle hot glassware with care to prevent burns.
• Dispose of waste materials safely according to laboratory guidelines.

• Define sublimation and triple point. (Sublimation: solid to gas phase transition without liquid phase. Triple point: the unique temperature and pressure at which solid, liquid, and gas coexist.)
• What is the difference between sublimation and desublimation? (Sublimation: solid to gas; desublimation: gas to solid.)
• Which compounds can be purified by sublimation? (Examples: camphor, benzoic acid, naphthalene, salicylic acid, quinine.)
• Why is ice used in the sublimation experiment? (It cools the vapor, allowing it to redeposit as pure crystals.)
• How can melting point determination confirm the purity of the sublimed product? (A pure substance has a sharp melting point close to its literature value, while impurities lower and broaden the melting point range.)