---
title: "A student uses paper chromatography to separate a mixture of two polar food dyes, Dye A and Dye B. The stationary phase is chromatography paper composed of cellulose, which contains numerous polar \\(-\\text{OH}\\) groups. The mobile phase is a polar mixture of water and ethanol. In the initial trial, Dye A travels near the solvent front with an \\(R_f\\) value of \\(0.75\\), while Dye B travels a shorter distance with an \\(R_f\\) value of \\(0.20\\). The student repeats the experiment using a new strip of the same cellulose paper and the same dye mixture, but mistakenly uses pure hexane, \\(\\text{C}_6\\text{H}_{14}\\text{(l)}\\) (a nonpolar solvent), as the mobile phase. Which of the following best predicts and explains the effect of this procedural error on the \\(R_f\\) values of the dyes?"
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url: "https://nerd-notes.com/ubq/123638/"
date_modified: "2026-09-28T12:01:52+00:00"
---

# A student uses paper chromatography to separate a mixture of two polar food dyes, Dye A and Dye B. The stationary phase is chromatography paper composed of cellulose, which contains numerous polar \(-\text{OH}\) groups. The mobile phase is a polar mixture of water and ethanol. In the initial trial, Dye A travels near the solvent front with an \(R_f\) value of \(0.75\), while Dye B travels a shorter distance with an \(R_f\) value of \(0.20\). The student repeats the experiment using a new strip of the same cellulose paper and the same dye mixture, but mistakenly uses pure hexane, \(\text{C}_6\text{H}_{14}\text{(l)}\) (a nonpolar solvent), as the mobile phase. Which of the following best predicts and explains the effect of this procedural error on the \(R_f\) values of the dyes?

A student uses paper chromatography to separate a mixture of two polar food dyes, Dye A and Dye B. The stationary phase is chromatography paper composed of cellulose, which contains numerous polar \(-\text{OH}\) groups. The mobile phase is a polar mixture of water and ethanol. In the initial trial, Dye A travels near the solvent front with an \(R_f\) value of \(0.75\), while Dye B travels a shorter distance with an \(R_f\) value of \(0.20\). The student repeats the experiment using a new strip of the same cellulose paper and the same dye mixture, but mistakenly uses pure hexane, \(\text{C}_6\text{H}_{14}\text{(l)}\) (a nonpolar solvent), as the mobile phase. Which of the following best predicts and explains the effect of this procedural error on the \(R_f\) values of the dyes?

- **A.** The \(R_f\) values of both dyes will increase because hexane has a lower boiling point and evaporates more rapidly, drawing the solutes upward at an accelerated rate.
- **B.** The \(R_f\) value of Dye B will increase to exceed that of Dye A because Dye B interacted less with the polar solvent and will therefore form stronger intermolecular attractions with the nonpolar hexane.
- **C.** The \(R_f\) value of Dye A will remain approximately \(0.75\) while the \(R_f\) value of Dye B will decrease to near \(0\), because Dye A has a smaller molar mass and travels with the solvent front independent of solvent polarity.
- **D.** The \(R_f\) values of both dyes will decrease to near \(0\), because the nonpolar hexane cannot form the strong dipole-dipole interactions or hydrogen bonds needed to overcome the attractions of the polar dyes to the cellulose stationary phase.

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