6 Questions
What is the definition of sublimation in physical chemistry?
The transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase.
What is the necessary condition for sublimation to occur?
The vapor pressure of the solid exceeds the ambient pressure at a specific temperature.
What is the purpose of using sublimation in pharmaceutical applications?
To purify volatile solids contaminated with non-volatile impurities.
What is the first step in the lyophilization procedure to purify a sublimed substance?
Place a mixture of 1 gm of the sublimed substance (impurity) in a 200 ml beaker, covered with a round bottomed flask filled with cold water or ice.
What is the physical state of the sublimed substance collected on the bottom of the cold flask and on the side walls of the beaker?
Pure, crystalline form.
What is the final step in the lyophilization procedure to purify a sublimed substance?
Collect the sublimed material in a small flask, weigh, and determine the M.P. of the pure substance.
Study Notes
Sublimation
- Sublimation is the transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase.
- Sublimation is an endothermic phase transition that occurs at temperatures and pressures below a substance's triple point.
Conditions for Sublimation
- Sublimation occurs when the vapor pressure of the solid exceeds the ambient pressure at a specific temperature.
Applications of Sublimation
- Pharmaceutical Applications: Sublimation is employed to purify volatile solids contaminated with non-volatile impurities.
- Drug Development: Sublimation is used in the lyophilization procedure.
Lyophilization Procedure
- Mix 1 gm of a sublimed substance (e.g. impurity naphthalene with sand) in a 200 ml beaker.
- Cover the beaker with a round bottomed flask filled with cold water or ice.
- Place the beaker on a hotplate or a low flame.
- The sublimed substance (e.g. naphthalene) will collect on the bottom of the cold flask and on the side walls of the beaker in pure, crystalline form.
- Scrape the sample of sublimed material from the flask and beaker.
- Collect the sample in a small flask, weigh, and determine the M.P. of the pure substance.
- Compare the results to the original sample.
Test your understanding of sublimation, a phase transition where a substance changes directly from solid to gas without going through the liquid phase. Learn about the conditions and characteristics of sublimation in organic chemistry.
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