Question

1. Which of the following solvents is considered the most polar? Which of the following solvents is considered least polar?

a.) Hexane

b.) Acetone

c.) 70% hexane–30% acetone

2. Which of the following compounds is considered the most polar?

a.) Chlorophyll-a

b.) Chlorophyll-b

c.) Carotene

3. When using column chromatography to separate the pigments in spinach, which solvent from Question 1 do you start with? Which solvent do you use next?

4. In no more than TWO sentences, explain why it is necessary to change the solvent composition during your column chromatography experiment.

Answer 1

1) Polar molecule is one which contain polar bond that is a bond which is formed between atoms of different electronegativity. Since there is large difference in electronegativity of carbon and oxygen, thus acetone is polar solvent and hexane is least polar because it doesn't contain any polar bond.

2) Chlorophylls are more polar than carotene because they contain polar bonds but since Chlorophyll b contain an additional CHO polar group as compared to methyl group in Chlorophyll a. Chlorophyll b is most polar.

3) Acetone is used as solvent in column chromatographic separation of pigments of spinach because it there polar nature.

4) Solvent composition is changed in column chromatography to elute various components present in the sample from the column.

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