Edexcel Jun 2015 Paper 4 Q16 (with explained solutions) |

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Edexcel Jun 2015 Paper 4 Q16

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16 Fresh coffee is made by adding hot water to ground coffee beans. Chemists at the University of Nevada have produced bio-diesel fuel from used coffee grounds. The grounds contain approximately 1015% oil by mass. This oil can be extracted, using standard chemical techniques, and then converted to bio-diesel by the reaction with methanol in the presence of a suitable catalyst. (a) (i) A solvent is added to the solid coffee grounds to dissolve the oil. Suggest how the oil is then obtained from this mixture. (2)(ii) Complete the equation below for the formation of a bio-diesel from the reaction of an oil with methanol. CH2OOCR(cid:97) 3CH3OH + CHOOCR(cid:97)(cid:97) CH2OOCR(cid:97)(cid:97)(cid:97) (iii) Suggest a suitable catalyst for the reaction in (a)(ii). (2) (1)22 *P42978A02228*<br />
*(b) Another source of oil for bio-diesel production is palm oil, obtained from the fruit of palm trees grown on large plantations across many tropical regions. Consider one advantage and one disadvantage of each source to decide which oil may provide a potentially greener and more sustainable supply of bio-diesel. (4)(Total for Question 16 = 9 marks) TOTAL FOR SECTION B = 48 MARKS *P42978A02328* 23 Turn over<br />

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Correct Answer Reject Mark recrystallise for 2nd mark 1st mark: Filter (off solid) / centrifuge (1) 2nd mark: (Fractionally) distil / evaporate ALLOW Just heat / steam distillation for 2nd mark (1) IGNORE Any other practical steps (e.g. separating funnel) Mark the two scoring points independently, but award (1) if filter is first mentioned after distil / evaporate / heat / steam distillation Correct Answer Reject Mark (1) (1) First mark for all three esters Second mark for structure of propane1,2,3-triol IGNORE Formulae written such as C3H5(OH)3 or C3H8O3 ALLOW CO2 or OCO for COO for ester linkage H3COOCR / CH3OOCR Mark independently Question Number 16 (a) (i) Question Number 16 (a) (ii)<br />
Question Number 16 (a) (iii) Correct Answer Reject Mark Sodium hydroxide / potassium hydroxide / NaOH / KOH / OH ALLOW sulfuric acid / H2SO4 or any other named strong acids or strong alkalis / HCl / just acid / just base / just alkali / just H+ Ni / nickel weak<br />
Question Number 16 (b) Correct Answer Reject Mark (1) Advantage of coffee grounds: 1st mark: For any mention of re-use of a resource or other listed advantages EXAMPLES TO LOOK FOR: Reuse of a waste material / less waste / no need to set up (new) coffee plantations / recycling Prevents using up landfill Coffee (plants / beans are ) renewable (resource) / can be re-grown NOTE renewable can score M3 as well if palm oil also described as renewable Coffee is widely-used (so grounds available) IGNORE Just coffee easier to grow / JUST doesnt require tropical conditions / doesnt require (extra) land Disadvantage of coffee grounds: 2nd mark: For any mention that coffee grounds made on a small-scale (so uneconomical) or other features listed below EXAMPLES TO LOOK FOR: Uses solvents / uses methanol / not carbon- neutral (from non-renewable resources such as crude oil) Only 1015% by mass of oil / has a low(er) yield of oil (than palm oil) ) if not awarded for M3 (Only made on a) small-scale so will not meet demand for biodiesel Coffee grounds distributed in small amounts (so will need collecting and transporting) ALLOW Costs of the use of solvents or energy required for extraction / energy required for distillation / energy required for purification or transport costs if not awarded for M4 (1)<br />
(1) Advantage of palm oil: 3rd mark: For any mention of palm oil being a plant-based / renewable / sustainable (resource) EXAMPLES TO LOOK FOR: Palm oil (made from plants that) can be re-grown / palm oil made from natural resources Palm oil (made from plants that are) renewable resources / palm oil made from sustainable resource NOTE renewable can score M1 as well if coffee also described as renewable Palm oil (made from plants that are) carbon- neutral / better carbon foot print / absorb CO2 IGNORE Just greener (already mentioned in question) ALLOW economic argument such as: Higher yield of oil (than in coffee grounds) if not already awarded for M2 Large scale production so economies of scale / more able to meet demand Fewer stages in its production (so more economical) Disadvantage of palm oil: 4th mark: For any mention of a disadvantage of a plant-based resource EXAMPLES TO LOOK FOR: Large scale plantations could lead to habitat loss Deforestation Loss of land (which should be used for food production) Only grows in hot/tropical climates High cost of transporting palm oil (from the tropical countries) if not already awarded for M2 Palm plants take a long time to grow TOTAL FOR QUESTION 16 = 9 marks) (1)<br />

Question 13 14 15 16 17

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