Organic Chemistry Laboratory RECRYSTALLIZATION The purpose of this experiment is

Question

Organic Chemistry Laboratory RECRYSTALLIZATION The purpose of this experiment is to enable the student to: 1. Learn about the practical and theoretical aspects of the recrystallization 2. Learn how to purify an impure solid by the simple technique of recrystallization, which involves several steps: (a) selecting the ideal solvent to accomplish such a purification. (b) dissolving the compound in the minimum amount of appropriate solvent while "boiling" hot. (c) filtering insoluble impurities while hot (if any are present) (d) crystallizing the purified compound (e) isolating the pure compound by vacuum filtration. (0 air drying pure compound. Figure 1. General Schematic of Recrystallization Process, After Appropriate Solvent Has Been Selected hot solvent paper clip e hot filter insolubls A SI II of hot solvent a si II hot plate A solid compound SI solid soluble impurity II solid insoluble impurity a dissolved compound si dissolved soluble imparity d) crytsallize compound by cooling solution Buchner fanncl watch glass o aspirator f) dry filter flask vacuam filter to solate crystals Pappus and Goicoechca-Pappas 3-1

Explanation / Answer

From what I gather , you need the theory for this experiment , so here is the principle of recrystallization :

Compounds acquired from natural sources or reaction mixtures nearly always have certain impurities. These may include mixture of insoluble, soluble, or colored impurities. For obtaining a pure compound these impurities are needed be seperated.
Recrystallization, which is also known as fractional crystallization, is a technique for purifying an impure compound in a solvent. This is based on the principle that the solubility of most solids increase with increase in temperature. It means that as temperature rises, the amount of solute that can be dissolved in a solvent generally increases. The process of recrystallization involves dissolving of the solid in an appropriate solvent at a raised temperature and the further re-formation of the purer crystals upon cooling, so that any impurities remain in solution.
The solvent chosen plays a pivotal role here. We know that "like dissolves like". Polar compounds are generally soluble in polar solvents and insoluble in nonpolar solvents, although nonpolar compounds are more soluble in nonpolar solvents.
So a good solvent must be chosen by running solvolysis experiment first. Almost all solids are more soluble in a hot than in a cold solvent, and solution crystallization takes advantage of this fact. Thus, if a solid is first dissolved in an amount of hot solvent insufficient to dissolve it when cold, crystals should form when the hot solution is allowed to cool. The extent of precipitation of the solid depends on the difference in its solubility in the particular solvent at temperatures between the extremes used. The upper extreme is determined by the boiling point of the solvent, whereas the lower limit is usually dictated by experimental convenience

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