chem lab questions easy point

2010-10-05 4:27 pm

1. outline a procedure for the recrystallization of benzoic acid that contains both a soluble and an insoluble impurity(using water as the solvent).

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It doesn't have to be long. A short one is good.

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己式庚辛

2010-10-05 6:59 pm

✔ 最佳答案

add some (slightly in excess) hot water to the sample and stir sufficiently.
filter the solution with stemless funnel and filter paper. if possible, warm the funnel.
slowly heat the filtrate to evaporate some water. when the benzoic acid is concentrate enough, let the solution cool.
(estimation of concentration / saturation: dipping a glass rod into solution, take it out and let it cool. if solid appears on the glass rod after cooling, the solution is concentrate enough.)
after cooling, solid pure benzoic acid should appear. filter, wash with minimal amount of cold water, let dry. done.

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