Paper chromatography

3 marks · Normal

In a chromatography experiment a spot of red dye moves 3.2 cm from the pencil line. The solvent front moves 6.4 cm from the pencil line.

Calculate the R_f value for the red 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

0.50 (±0.01)

Common mistakes: using solvent distance as numerator

Show mark scheme and worked solution

Marking points

M1 · 1 mark · Writes or uses correct formula for R_f (distance moved by spot / distance moved by solvent front)

M2 · 1 mark · Substitutes correct values: 3.2/6.4

A1 · 1 mark · Calculates correct value: 0.50 (to 2 decimal places; accept 0.5 if clearly from working) (follow-through)

Worked solution

R_f = (distance moved by spot) / (distance moved by solvent front)

R_f = 0.50