GCSE Chemistry Required Practical: Calculating Retention Factors

Key Stage 4

Meaning

Use a Chromatography experiment to produce a Chromatogram and calculate the Retention Factors (R_f) for they dyes found within different inks.

Method

1. Take a piece of chromatography paper of width 6cm and height 10cm.
2. Using a ruler draw a line with pencil across the width 2cm up from the end.
3. Add a dot of each unknown sample on the pencil line at 1cm intervals.
4. Suspend the chromatography paper in a suitable solvent just below the pencil line with most of the paper above the solvent.
5. Wait until the solvent stops rising up the paper.
6. Use a ruler to measure the distance that the solvent has traveled up the paper.
7. Use a ruler to measure the distance that the different dyes have traveled up the paper.
8. Use the following equation to find the Retention Factor for each dye:

\[R_f = \frac{d_c}{d_s}\]

Where:

R_f = Retention Factor

d_c = distance moved by the chemical

d_s = distance moved by the solvent