GCSE Chemistry Required Practical: Calculating Retention Factors
Key Stage 4
Meaning
Use a Chromatography experiment to produce a Chromatogram and calculate the Retention Factors (Rf) for they dyes found within different inks.
Method
- Take a piece of chromatography paper of width 6cm and height 10cm.
- Using a ruler draw a line with pencil across the width 2cm up from the end.
- Add a dot of each unknown sample on the pencil line at 1cm intervals.
- Suspend the chromatography paper in a suitable solvent just below the pencil line with most of the paper above the solvent.
- Wait until the solvent stops rising up the paper.
- Remove the paper from the solvent and draw a pencil line at the boundary between the dry and wet areas, then leave the paper to dry completely.
- Use a ruler to measure the distance that the solvent has traveled up the paper.
- Use a ruler to measure the distance that the different dyes have traveled up the paper.
- Use the following equation to find the Retention Factor for each dye
\(R_f = \frac{d_c}{d_s}\)
- Where:
- Rf = Retention Factor
- dc = distance moved by the chemical
- ds = distance moved by the solvent