Paper chromatography

3 marks · Normal

In a paper chromatography experiment, the solvent front moved 8.2 cm from the pencil line. One of the dyes in a mixture moved 5.3 cm from the pencil line.

Calculate the Rf value for this dye. Show your working.

Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.

Show answer

0.65 (±0.01)

Also accept: 0.646; 0.65 (to 2 dp)

Common mistakes: 5.3/8.2 = 1.55 (reversed division)

Show mark scheme and worked solution

Marking points

M1 · 1 mark · Writes correct formula for Rf value.

M2 · 1 mark · Substitutes correct values from the question (5.3 cm for spot, 8.2 cm for solvent).

A1 · 1 mark · Correct final value calculated: Rf = 0.65 (to 2 decimal places, 0.01 tolerance).

Worked solution

The formula for Rf value is:

Distance moved by spot = 5.3 cm

Distance moved by solvent front = 8.2 cm

Rf value (to 2 significant figures) is 0.65.