I In purification by recrystallization experiment: ) Two students recystallize 1
ID: 705774 • Letter: I
Question
I In purification by recrystallization experiment: ) Two students recystallize 10.0 g samples of benzoic acid from water, the first one dissolve the acid at 95 C and filter it (Vacuum filtration) at 18 C, while the second one dissolve it at 80 C and filter it (Vacuum filtration) at 10 C . Calculate the was required to use and the amount of pure acid obtained by each one by completing the following table. (1 point) quantity of water each student Temp. Solublity of Quantity of Quantity of Amount of Amount of pure (C) benzoic acid in water needed water needed pure acid acid obtaind by (g/100)ml by the first by the second obtaind by the the second 102ter student (ml) |student (ml-first student (g) | student (g) 10 18 80 95 6.80 0.21 0.27 2.75 2) Why is it important to minimize evaporation during the gravity filtration of the hot solution? (0.25 point) 3) What advantages does water have as a solvent? (0.25 point) 4) What advantages does carbon tetracholnde have over benzene as a solvent? (0.25 point) 5) What advantages does ethyl alcohol over octyl alcohol as a solvent? (0.25 point) II- In isolation of caffein experiment: 1) What is the disadvantage of using an extraction solvent whose density is approximately the same as that of water? (0.25 point)Explanation / Answer
2) it is important to minimise evaporation un order to have correct results.
3) advantages of water as solvent are
a) it does not change temperature rapidly
b)itt is non toxic to breathe
c) It is nonflammable
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