Name: ________________________ Class: ________________________ Date: ________________________ Chromatography Time: 72 minutes Marks: 68 marks Comments: Page 1 of 25 Q1. The diagram shows a chromatogram for a food colouring. (a) How does the chromatogram show that the food colouring is a mixture? ___________________________________________________________________ ___________________________________________________________________ (1) (b) A student makes measurements for spot C. The table shows the results. Distance in mm Distance moved by spot C 7 Distance moved by solvent 39 Calculate the Rf value for spot C. Give your answer to 2 significant figures. Use the results in the table. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ Rf value = ____________________ (3) Page 2 of 25 (c) Plan a chromatography experiment to investigate the colours in an ink. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ (6) (Total 10 marks) Page 3 of 25 Q2. A student used paper chromatography to investigate the colours in different inks. Figure 1 shows the apparatus the student used. Figure 1 (a) The student made two mistakes in setting up the apparatus. Identify the two mistakes. Describe the problem each mistake would cause. Mistake 1 __________________________________________________________ Problem __________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ Mistake 2 __________________________________________________________ Problem __________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ (4) Page 4 of 25 (b) The student then set up the apparatus without making any mistakes. Figure 2 shows his results. Figure 2 What colours are in the black ink? ___________________________________________________________________ ___________________________________________________________________ (1) (c) Which of the inks is the most soluble in the solvent? Give a reason for your answer. Ink _____________________________________________________________ Reason ___________________________________________________________ ___________________________________________________________________ (2) Page 5 of 25 (d) Use Figure 2 to complete the table below, then calculate the Rf value for red ink. Distance in mm Distance moved by red ink ________________________ Distance from start line to solvent front ________________________ The Rf value for red ink is calculated using the equation. Rf = Give your answer to two significant figures. ___________________________________________________________________ ___________________________________________________________________ Rf value = _____________________________ (5) (e) How can you tell from Figure 2 that the Rf value for the blue ink is greater than the Rf value for the red ink? ___________________________________________________________________ ___________________________________________________________________ (1) (Total 13 marks) Page 6 of 25 Q3. Race horses may be given drugs to improve their performance in races. This is illegal in the UK. After races, urine samples are collected from the horses. These samples are tested for drugs. Chromatography is one of the tests used to identify drugs in urine. The diagram shows a chromatogram. (a) How do we know that sample 1 was a pure sample of caffeine? ___________________________________________________________________ ___________________________________________________________________ (1) Page 7 of 25 (b) Calculate the Rf value for cocaine. Give your answer to 2 significant figures. Use information from the diagram. Use the equation: ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ Rf value of cocaine = ____________________ (4) (c) Give three conclusions about the urine sample from the horse. Use information from the diagram. 1. _________________________________________________________________ ___________________________________________________________________ 2. _________________________________________________________________ ___________________________________________________________________ 3. _________________________________________________________________ ___________________________________________________________________ (3) (Total 8 marks) Page 8 of 25 Q4. Chromatography can be used to find out what substances a drug contains. The diagram shows a chromatogram for seven different drugs. (a) Calculate the Rf value of drug G. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ Rf value = ____________________ (4) (b) Describe what the diagram shows about drug D. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ (3) Page 9 of 25 (c) Which substance is most soluble in the solvent used in this chromatogram? Give a reason for your answer. ___________________________________________________________________ ___________________________________________________________________ (1) (d) Explain the result for drug F. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ (2) (Total 10 marks) Page 10 of 25 Q5. This question is about mixtures. (a) Which substance is a mixture? Tick (✓) one box. Air Gold Methane Nitrogen (1) (b) Food colourings are often mixtures of dyes. What name is given to mixtures that are designed as useful products? ___________________________________________________________________ (1) A student investigated a purple food colouring, Y, using chromatography. The student compares Y with dyes A, B and C. (c) Figure 1 shows the apparatus used. Figure 1 Page 11 of 25 Chromatography involves a stationary phase and a mobile phase. Draw one line from each phase to what is used for that phase. Use Figure 1. Phase What is used Beaker Mobile phase Chromatography paper Food colouring Stationary phase Pencil line Solvent (2) Figure 2 shows the student’s results. Figure 2 (d) What three conclusions can you make about the dyes in food colouring Y? 1. _________________________________________________________________ ___________________________________________________________________ 2. _________________________________________________________________ ___________________________________________________________________ 3. _________________________________________________________________(3) Page 12 of 25 (e) In a different experiment a student recorded these results: Distance moved by dye G = 60 mm Distance moved by solvent = 80 mm Calculate the Rf value of dye G. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ Rf = _______________ (2) (Total 9 marks) Page 13 of 25 Q6. A student used paper chromatography to identify the colours in a black ink. The diagram below shows the student’s results. (a) What colours are in the black ink? ___________________________________________________________________ ___________________________________________________________________ (2) (b) Suggest which colour is least soluble in the solvent. Give a reason for your answer. Colour ______________________ Reason __________________________________________________________ ___________________________________________________________________ (2) Page 14 of 25 (c) Use the diagram above to complete the table below. Distance in mm Distance moved by green colour Distance moved by solvent Calculate the Rf value for the green colour. Use the equation: ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ Rf value = ________________________ (4) (Total 8 marks) Page 15 of 25 Q7. (a) This question is about gases. Draw one line from each substance to the description of the substance. (3) Page 16 of 25 (b) What is used to test for each of the gases? Draw one line from each substance to the description of the substance. (2) (c) Give two reasons why the percentage of carbon dioxide in the air has decreased in the last 2.7 billion years. Tick (✓) two boxes. Combustion Dissolved in oceans Intense volcanic activity Photosynthesis Respiration (2) Page 17 of 25 Oxygen reacts with sulfur dioxide. The reaction is reversible. (d) What is the symbol for a reversible reaction? _________________________ (1) (e) Complete the sentence. In a reversible reaction the forward reaction is exothermic, so the reverse reaction is _________________________ . (1) (f) A reversible reaction happens in apparatus which stops the escape of reactants and products. Complete the sentence. Equilibrium is reached when the forward and reverse reactions happen at exactly the same _________________________ . (1) (Total 10 marks) Page 18 of 25 Mark schemes Q1. (a) more than 1 dot in a vertical line 1 (b) correct equation and substitution 7/39 accept Rf = distance moved by spot C / distance moved by solvent 1 calculation and answer 0.1795 1 answer to 2 significant figures 0.18 1 (c) Level 3: The plan would lead to the production of a valid outcome. All key steps are identified and logically sequenced. 5-6 Level 2: The plan would not necessarily lead to a valid outcome. Most steps are identified, but the plan is not fully logically sequenced. 3-4 Level 1: The plan would not lead to a valid outcome. Some relevant steps are identified, but links are not made clear. 1-2 No relevant content 0 Indicative content • put dots of known colours, and a dot of the ink on a pencil line on the chromatography paper. • place the bottom of the paper in water, making sure the start line is above the water • leave for solvent to rise up through paper. • when solvent near top of paper, remove and leave to dry. • compare positions of dots for known colours with those from ink 6 [10] Q2. (a) start line drawn in ink 1 Page 19 of 25 (so) line would run 1 start line below solvent level 1 (so) samples would wash off 1 (b) red and blue both colours needed 1 (c) yellow 1 travels furthest up the paper 1 (d) distance moved by red ink 13 ±1 measurements in cm max 1 mark for mps 1 and 2 1 distance from start line to solvent front 44 ±1 1 correct substitution 1 allow ecf from Table 4 correct answer 1 range if correct is 0.27 to 0.33 to 2 significant figures 1 (e) moves further or nearer the top of the paper 1 [13] Q3. (a) only one spot (on the chromatogram) 1 (b) (distance moved by substance =) 4.2 (cm) and (distance moved by solvent =) 9.4 (cm) allow in range 4.0–4.4 (for substance) 1 1 0.4468 1 0.45 Page 20 of 25 allow answer in range 0.43 to 0.47 1 (c) (made of) three substances 1 two are unknown 1 one is cocaine 1 [8] Q4. (a) 1 5.1 ± 0.1 cm and 6.8 ± 0.1 cm both measurements from figure 1 1 0.75 allow answer in range 0.72–0.77 allow ecf from incorrect measurements to final mark for 3 marks an answer in range of 0.72–0.77 scores 4 marks 1 (b) drug D contains one of the substances in E 1 drug D contains drug B 1 (and) a compound not found in any of the other drugs allow an unknown substance if no other marks awarded allow 1 mark for it is a mixture/ impure or it contains three substances 1 (c) A as it has travelled the furthest in the solvent ignore A unqualified 1 (d) spot has stayed on the start line 1 (because) it is insoluble 1 [10] Page 21 of 25 Q5. (a) air 1 (b) formulation(s) 1 (c) 1 additional line from a box on the left negates the mark for that box 1 (d) allow colour for dyes Y contains 3 dyes 1 Y contains 2 known dyes allow Y contains A and C 1 Y contains an unknown dye allow Y does not contain dye B 1 alternative approach: Y contains 3 dyes (1) Y contains 1 known dye (1) allow Y contains dye C Y contains 2 unknown dyes (1) allow Y does not contain dyes A and B (e) (Rf =) 1 Page 22 of 25 = 0.75 ignore units 1 [9] Q6. (a) red and blue 1 unknown 1 both needed for the mark (b) red ignore black 1 travels least far dependent on correct colour allow closest to the start line 1 (c) distance moved by green colour = 12 mm allow 10 to 14 mm 1 distance moved by solvent = 36 mm allow 35 to 36 mm 1 allow correct substitution of student’s measurements 1 Rf value = 0.33 allow correct answer from student’s measurements for 2 marks 1 [8] Q7. Page 23 of 25 (a) If more than one line is drawn from any one substance and not crossed out, no mark is given for that substance. The other marks can be awarded. 1 1 1 (b) If more than one line is drawn from any one gas and not crossed out, no mark is awarded for that gas. The other mark can be awarded. 1 1 (c) dissolved in oceans 1 photosynthesis 1 (d) ⇌ ignore any other words, formulae or symbols Page 24 of 25 1 (e) endothermic (reaction) spelling must be correct do not accept exothermic 1 (f) rate (of reaction) allow speed or velocity do not accept any other response 1 [10] Page 25 of 25