Question

Based on how the polarity of a molecule affects its solubility in the solvent, and thus how it moves up the paper, if you were to use water as the solvent in this chromatography experiment, what results would you obtain? Would the four pigments separate in the same way? Explain your reasoning.

Answer 1

In paper chromatography, all have a stationary phase (a solid, or a liquid supported on a solid) and a mobile phase (a liquid or a gas). The mobile phase flows through the stationary phase and carries the components of the mixture with it. If you use water as the mobile phase and the water bound on to the cellulose ( main component of paper chromatography)  as the stationary phase, there can't be any meaningful difference between the amount of time a substance spends in solution in either of them. The complication arises because the cellulose fibres attract water vapour from the atmosphere as well as any water that was present when the paper was made. All substances should be equally soluble (or equally insoluble) in both. Partition only happens between solvents which don't mix with each other. Thus the four pigments would not separate in the same way.