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Final_Study_Questions_Key_II

# Final_Study_Questions_Key_II - Final Study Questions Key...

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Final Study Questions Key Part II Solubility: 1. The following table summarizes the solubility of the amino acid DL-alanine in water. Solubility (g/100 mL water) Temperature ( o C) 44 100 32 75 23 50 17 25 12 0 (a) Give a brief procedure for recrystallizing 100 grams of impure DL-alanine. Answer: Dissolve the impure solid in the minimum amount of boiling water, set aside and let cool slowly to room temperature. Place in an ice bath to chill to 0 o C. Filter the solid product using vacuum filtration. Rinse the solid with the minimum amount of chillled (0 o C) water. (b) What is the maximum amount of product you could recover in the recrystallization from water? Answer: Maximum percent recovery = 44 - 12 44 = 72.7% If the impure product were free of impurities, the maximum amount that could be recovered would be 72.7g. Since there are impurities, less will be recovered. (c) If the solubility of DL-alanine in an ethanol-water solution that is 25% ethanol is 3.84 g/100mL solution, how could you improve your recovery in the recrystallization in question (b)?

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