Purity, formulations and chromatography

9.The student repeated the investigation using ethanol as the solvent. The blue dye is not soluble in ethanol. The yellow dye is more soluble in ethanol than in water. Which two statements about the resulting chromatogram are correct? (Select two)

10.A group of students investigated the purity of water samples. Their boiling points are: A 103°C, B 105°C, C 101°C, D 102–106°C. Which sample is the purest?

11.A student carried out chromatography on green ink. The solvent front moved 5.8 cm and the yellow dye moved 4.5 cm. Calculate the Rf value of the yellow dye to 2 significant figures.

12.A chromatogram was produced from samples A–E and black food colouring. Which of the following conclusions is not true for this chromatogram?

13.What is a formulation?

14.Which of the following statements about paper chromatography are correct? (Select all that apply)

15.A pure substance will produce only one spot on a chromatogram.

16.Impurities lower the melting point and raise the boiling point of a substance.

17.The Rf value of a substance is always the same regardless of the solvent used.

18.In paper chromatography, the start line should be drawn in ink.

19.A formulation is a mixture that has been designed as a useful product.

20.What is the mobile phase in paper chromatography?

21.Which of the following best describes a mixture?

22.Which of the following is not a formulation?

23.Which of the following are correct about formulations? (Select all that apply)

24.Match each term with its correct description.

25.Match each chromatography term with its correct definition.

26.Place the steps of the paper chromatography practical in the correct order.

27.Which of the following statements about a mixture are correct? (Select all that apply)

28.Match each separation technique to the mixture it is used to separate.

29.Place the main stages used to make fresh water potable into the correct order.

30.A student uses paper chromatography to separate a mixture of dyes. Which of the following statements about the process are correct? (Select all that apply)

31.A student runs a chromatogram and measures the distance from the baseline to the centre of a spot as 3.0 cm and the distance from the baseline to the solvent front as 6.0 cm. Which of the following is the Rf value of the spot?

32.Which of the following are formulations? (Select all that apply)

33.In a chromatogram, sample P produces a single spot with the same Rf value as a spot from an unknown mixture U. Which conclusion is correct?

34.Deionised water is used in chemical analysis because dissolved ions could react with the substances being tested and give a false result.

35.A student heats a sample of an unknown solid. It begins to melt at 78°C and finishes melting at 85°C. What does this tell you about the sample?

36.A sample of impure water is found to have a boiling point of 102°C. Which statement explains this?

37.A chromatogram of an unknown mixture U shows spots with Rf values 0.25 and 0.60. Reference substances have Rf values: A = 0.25, B = 0.45, C = 0.60. Which substances are present in U?

38.Match each separation technique with the mixture it is used to separate.

39.In paper chromatography, why is the pencil line drawn on the chromatography paper rather than using ink?

40.A student sets up paper chromatography but forgets to add a lid to the beaker. What is the most likely effect on the chromatogram?

41.Complete the sentence about the everyday meaning of a pure substance.

42.What name is given to a product such as methylated spirit, which is a mixture designed as a useful product?

43.Complete the sentence about the phases in paper chromatography.

44.In a chromatogram, a colour from dye A moves 3.6 cm and the solvent moves 8.0 cm. Calculate the Rf value for the colour from dye A. Give your answer to 2 significant figures.

45.A yellow dye moves 4.8 cm and the solvent moves 6.0 cm. Calculate the Rf value of the yellow dye. Give your answer to 2 significant figures.

46.A sample of methylated spirit contains 260.5 g ethanol, 25.3 g methanol, 2.5 g pyridine and 1.0 g methyl violet. Calculate the percentage by mass of ethanol in the sample. Give your answer to 2 significant figures.

47.Complete the sentence about Rf values.

48.What is the name given to the visual output of a chromatography run, which is the piece of chromatography paper with visibly separated components?

49.What term describes a mixture that has been designed as a useful product, such as paint or medicine?

50.Name the phase in paper chromatography that is the solvent in which the sample molecules move.

51.A dye in a chromatogram travels 4.5 cm from the baseline while the solvent front travels 7.5 cm from the baseline. Calculate the Rf value of the dye. Give your answer to 2 significant figures.

52.Complete the sentences about using melting points to judge purity. Use the words: sharp, lower, higher.

53.Aspirin tablets contain aspirin as the active ingredient and other inactive ingredients. Suggest the reason for adding a flavouring to the tablet.

54.Why could the green ink not be described as a pure substance?

55.The sample of methylated spirit was analysed and found to contain small amounts of other substances not stated in the formulation. Suggest how this may affect the performance of the formulation.

56.Give two examples of formulations used in different industries.

57.Explain what the term ‘pure’ means in chemistry and compare it to the everyday meaning.

58.In a chromatogram, a colour from dye A moves 3.6 cm and the solvent moves 8.0 cm. Calculate the Rf value for the colour from dye A. Give your answer to 2 significant figures.

59.A yellow dye moves 4.8 cm and the solvent moves 6.0 cm. Calculate the Rf value of the yellow dye. Give your answer to 2 significant figures.

60.A sample of methylated spirit contains 260.5 g ethanol, 25.3 g methanol, 2.5 g pyridine and 1.0 g methyl violet. Calculate the percentage by mass of ethanol in the sample. Give your answer to 2 significant figures.

61.A dye in a chromatogram travels 4.5 cm from the baseline while the solvent front travels 7.5 cm from the baseline. Calculate the Rf value of the dye. Give your answer to 2 significant figures.