1. What is the purpose of the cotton and the sand at the bottom of the chromatog

Question

1. What is the purpose of the cotton and the sand at the bottom of the chromatography column? 2. Why is it important not to let the column go dry? 3. What is the purpose of the sand at the top of the column? 4 What is the theoretical yield of fluorenone if you oxidize 100 mg of fluorene? 5. List 3 experimental parameters you could alter to improve a poor column chromatographic separation. a) b) c) 6. Why do you collect quite a few small fractions (3 mL each) rather than only a few larger fractions (e.g.. 20 mL)? 7. If you separate a mixture of o-cresol and 1-methoxy-3-methylbenzene by column chromatography, which compound elutes first and why?

Explanation / Answer

1) this ia done in order to prevent loss of stationary phase out of the bottom.

2)because if let your column dry, silica gel starts to crack and thus you will get poor separation of compounds.

3)sand at top of column prevent disruption of sample when solvent is added the column.,or in other words it protects the shape of the sample when solvent is added.

4)   C13H10 + O2 = C13H8O + H2O

moles of C13H10 present = mass /MW = 0.1 g/166g/mol = 0.000602 moles

So theoretical yield of C13H8O = 0.000602 mol x 180g/mol = 0.108 g of C13H8O

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