AP Chemistry
3.9 Separation of Solutions and Mixtures
3.1 Intermolecular and Interparticle Forces
A student investigates the separation of three food dyes, Dye 1, Dye 2, and Dye 3, using paper chromatography. The stationary phase consists of cellulose paper containing numerous polar hydroxyl (\(-\text{OH}\)) groups. The student spots a mixture of the three dyes onto two identical chromatography strips and develops them separately: one in Solvent 1 (pure hexane, a nonpolar solvent) and the other in Solvent 2 (a mixture of ethanol and water, a polar solvent). The retention factor (\(R_f\)) values for each dye in both solvents are shown in the table below.
Based on the data, which of the following correctly ranks the dyes in order of greatest to least affinity for the stationary phase, and provides the best explanation for the change in the \(R_f\) value of Dye 1 when changing from Solvent 1 to Solvent 2?
| Dye | \(R_f\) in Solvent 1 (Hexane) | \(R_f\) in Solvent 2 (Ethanol-Water) |
|---|---|---|
| Dye 1 | \(0.12\) | \(0.85\) |
| Dye 2 | \(0.45\) | \(0.68\) |
| Dye 3 | \(0.88\) | \(0.22\) |
Based on the data, which of the following correctly ranks the dyes in order of greatest to least affinity for the stationary phase, and provides the best explanation for the change in the \(R_f\) value of Dye 1 when changing from Solvent 1 to Solvent 2?
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