Chemistry · Oct / Nov 2016 · Paper 11 · Question 3

A paper chromatography experiment is carried out to find an $R_f$ value for Fe$^{3+}$(aq). The result is shown. [diagram: chromatogram with solvent front, starting line, spot labelled Fe$^{3+}$, distances $x$ and $y$] To make the spot containing Fe$^{3+}$(aq) more visible, the paper is sprayed with aqueous sodium hydroxide so that a precipitate of iron(III) hydroxide forms. Under the conditions of the experiment, the $R_f$ of Fe$^{3+}$(aq) is given by ......1...... and the colour of the precipitate is ......2...... . Which row correctly completes gaps 1 and 2?

1. A$\dfrac{x}{y}$ red-brown
2. B$\dfrac{x}{y}$ green
3. C$\dfrac{y}{x}$ red-brown
4. D$\dfrac{y}{x}$ green

As printed in the paper