Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Section
Paper chromatography
21 practice questions
Practice questions
1–10 of 21
Question 1
1 mark · Easy
Answer and see the solution →State which part of the chromatography paper you should draw the starting line on before adding the sample in a paper chromatography experiment.
Question 2
3 marks · Easy
Answer and see the solution →The chromatogram below was obtained by separating a mixture of food dyes A and B. The solvent front travelled 6.0 cm from the pencil line. The diagram shows the position of the spots:
Chromatogram of food dyes A and B (a) State how the R_f value for dye B can be calculated. [1]
(b) Calculate the R_f value for dye B. Give your answer to two decimal places. [2]
(a)[1 mark]State how the R_f value for dye B can be calculated.
(b)[2 marks]Calculate the R_f value for dye B. Give your answer to two decimal places.
Question 3
2 marks · Easy
Answer and see the solution →In a paper chromatography experiment, the pencil line was drawn 1.0 cm from the bottom of the paper. The solvent front travelled 7.2 cm from the pencil line, and a blue dye moved 5.0 cm from the pencil line. Calculate the R_f value for the blue dye.
Question 4
2 marks · Easy
Answer and see the solution →Explain why two different dyes can have the same colour but different R_f values in paper chromatography.
Question 5
3 marks · Easy
Answer and see the solution →A student is testing three samples using paper chromatography. The chromatogram below shows the positions of the spots after the experiment was completed. The solvent front moved 9.0 cm from the pencil line.
Chromatogram with three samples and a solvent front (a) Which sample travelled furthest from the pencil line? [1]
(b) Calculate the R_f value for sample Y. [1]
(c) Explain what a high R_f value tells you about a dye's solubility in the solvent. [1]
(a)[1 mark]Which sample travelled furthest from the pencil line?
(b)[1 mark]Calculate the R_f value for sample Y.
(c)[1 mark]Explain what a high R_f value tells you about a dye's solubility in the solvent.
Question 6
1 mark · Easy
Answer and see the solution →How should you measure the distance a dye has travelled on a chromatogram to calculate its R_f value?
Question 7
3 marks · Easy
Answer and see the solution →Describe how you would carry out a paper chromatography experiment to determine if a black ink contains more than one dye. Include three steps in your description.
(a)[1 mark]Step 1:
(b)[1 mark]Step 2:
(c)[1 mark]Step 3:
Question 8
2 marks · Easy
Answer and see the solution →A scientist measures the distance from the pencil line to the centre of a dye spot as 2.5 cm and the distance from the pencil line to the solvent front as 7.8 cm. Calculate the R_f value for this dye. Give your answer to two decimal places.
Question 9
2 marks · Normal
Answer and see the solution →State what is meant by the term "Rf value" in paper chromatography, and explain why the Rf value is always less than 1.
Question 10
4 marks · Normal
Answer and see the solution →The following steps outline a method to separate a mixture of food colourings using paper chromatography.
(a)[1 mark]Name the purpose of drawing the line in pencil at the bottom of the chromatography paper.
(b)[1 mark]Explain why it is important that the solvent level in the beaker is below the pencil line.
(c)[1 mark]Describe what you would observe on the paper after the experiment if the mixture contained three different dyes.
(d)[1 mark]State one safety precaution you should take when carrying out this experiment.