Question Constellation Sign up for free

AQA · GCSE · Chemistry · Higher

Dye purity comparison by chromatography

Q04.3 2 marks

Figure 4 shows the results of Experiment 1 and Experiment 2 using orange dye A.

Figure 4
Figure 4

Figure 4

Enlarged question image

Figure 4

The student investigated a different orange dye (B). Figure 5 shows the results of Experiment 3 using orange dye B.

Figure 5
Figure 5

Figure 5

Enlarged question image

Figure 5

Compare the purity of the orange dyes A and B. Give reasons for your answer. Use Figure 4 and Figure 5.

Write your answer first. You can study the marking guidance whenever you need it.

Answer this question
Study the marking See what earns credit and compare it with a full-mark answer.

Marking points

  1. 1 Compares both dyes: A is impure/a mixture and B is pure.
  2. 2 Justifies the comparison using the chromatograms: A gives two spots/components while B gives one.

Full-mark answer

Dye A is impure, or a mixture, because it separates into two spots, showing two dyes. Dye B is pure because it produces only one spot.

Why this answer loses marks

Dye B is purer because its spot is a different distance from the start line.

Purity is inferred from the number of separated spots, not from how far a spot travels.

Answer this question