orgo - Conclusion Essentially did you achieve your...

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Conclusion Essentially, did you achieve your purpose (look at your brief statement of purpose for prelab)? State what the eutectic temperature and composition at eutectic point was for your mixture of urea and cinnamic acid. State what your unknown was. Recrystallization Experiment Crystallization Sketch of apparatus: Fig. 4.1, 4.3, 4.15 Crystallization: a method to purify solids 4 important concepts to consider in the process of recrystallization - solubility - saturation level - exclusion - nucleation Read details on how these concepts are employed and what is involved on pg. 61 Example of crystallization in the human body: kidney stones Most common component is calcium oxalate Soluble in urine and blood Saturation level goes up with Nucleation on calcium phosphate Impurities in solids can result from reactions: -side products, unreacted starting materials, inorganic materials, solvents From storage: - decomposition, contamination from other chemicals Impurities may be trapped within the crystal lattice or on the surface of the solid. Seven steps of crystallization Remember: like dissolves like - polar solvents dissolves polar solutes, nonpolar solvents dissolves nonpolar solutes Polarity and Solubility of Organic compound affected by: molecular weight if comparing compounds with the same functional group (lower, more soluble) and proportion of hydrocarbon in molecule to functional group within the molecule (higher proportion, lower polarity) 1) Choosing solvent and solvent pairs Ideal characteristics for solvent with respect to solute - Dissolves the solute completely when solvent is hot (at boiling point of solvent) - Precipitates solute completely when solvent is cold (if you use a solvent that does not do this (i.e. wrong solvent), you will have
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- does not react with solute Back to like dissolves like - if solute and solvent are too similar in polarities, solute will
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  • Spring '09
  • Govindarajoo
  • Solubility, Solvent, Crystal, solvent pairs

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