Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Chapter
Elements, Compounds and Mixtures
69 practice questions
Topics covered
Practice questions
51–60 of 69
Question 51
1 mark · Normal
Answer and check →Which of these would not be a correct safety precaution for a paper chromatography experiment using organic solvents?
- A.Wear gloves when handling solvents.
- B.Use a well-ventilated area.
- C.Taste the dyes after the experiment.
- D.Avoid contact of solvent with skin.
Question 52
2 marks · Normal
Answer and see the solution →Give two reasons why different dyes in a mixture travel different distances up the paper in chromatography.
Question 53
4 marks · Normal
Answer and see the solution →You want to check whether a green dye in a drink is a single substance or a mixture of dyes. You will use paper chromatography to investigate.
(a)[2 marks]Describe how you would set up and carry out this experiment, naming all key steps.
(b)[2 marks]Explain how you would use the chromatogram to decide if the green dye is pure or a mixture.
Question 54
2 marks · Normal
Answer and see the solution →State two reasons why the line for the origin is drawn with pencil, not pen, in a paper chromatography experiment.
Question 55
4 marks · Normal
Answer and see the solution →A student uses paper chromatography to separate a mixture of coloured dyes. The chromatogram below shows the results. The student also spotted two known dyes, X and Y, on the same piece of chromatography paper.
Chromatogram from a mixture and two known dyes Spots shown on chromatogram Sample Distance moved from origin (cm) Mixture (green) 4.8 Dye X (blue) 1.7 Dye Y (orange) 4.8 Solvent front 6.0 (a)[2 marks]State which dye(s), X or Y, is present in the mixture. Give a reason for your answer.
(b)[2 marks]Explain why the blue spot (Dye X) did not reach as far up the paper as the orange spot (Dye Y).
Question 56
3 marks · Normal
Answer and see the solution →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.
Question 57
2 marks · Hard
Answer and see the solution →A blue dye in a chromatography experiment travels 1.5 cm from the pencil line. The solvent front moves 5.0 cm from the pencil line. Calculate the R_f value for the blue dye. Show your working.
Question 58
5 marks · Hard
Answer and see the solution →A student wants to find out whether the green colour in a piece of candy is due to a single dye or a mixture of dyes. Describe how you would carry out a paper chromatography experiment to investigate this. Include details about:
(a)[1 mark]the preparation of the chromatography paper and application of the sample
(b)[1 mark]how to set up and run the chromatography
(c)[1 mark]how to mark the solvent front and why this is important
(d)[1 mark]what you would expect to observe if the green dye is a mixture of dyes
(e)[1 mark]one step you should take to make sure your results are reliable
Question 59
2 marks · Hard
Answer and see the solution →Explain why the R_f value must always be between 0 and 1 in a paper chromatography experiment.
Question 60
5 marks · Easy
Answer and see the solution →A student finds a mixture of iron filings and sulfur powder. She wants to investigate how to classify and separate these substances.
(a)[2 marks]State whether iron, sulfur, iron sulfide, and a mixture of iron and sulfur are elements, compounds or mixtures.
(b)[1 mark]Describe a physical method you could use to separate the iron filings from the sulfur powder in the mixture.
(c)[2 marks]Explain why you cannot separate iron sulfide into iron and sulfur by a physical method.