Question

48. Chlorophyll a is slightly smaller and forms fewer hydrogen bonds with the paper than chlorophyll b due to the differences between the two molecules that are shown in red circle in Figure 1 above. How would this affect the chromatography in these two pigments?

Answer 1

The chromatography you're talking about is Thin layer chromatography.
It is the simplest of the chromatographic methods. It consists in placing on a sheet (paper, silica or other) a stain and let it elute by soaking it in a solvent or a mixture of solvent (called eluent), the eluent diffuses along the support. The stain migrates on the leaf more or less quickly depending on the nature of the interactions it undergoes on the part of the support and the eluent.

*If the chlorophyll a is smaller, it means it can move faster in the sheet (stationary phase) by capillarity.
*If the chlorophyll a has fewer hydrogen bonds, it means he's not very attached to the sheet, which let the chlorophyl move faster, and being eluted.

*The chlorophyll b is a bigger molecule and has more hydrogen bonds, so it moves slowly in the sheet. That's why we can see a difference between the two chlorophylls in the chromatography separation.