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

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Edexcel Jun 2015 (IAL) Paper 4 Q16

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16 Chemists in Asia have been investigating the use of a range of non-edible seeds to produce oil for bio-diesel production, instead of using edible oils. The oils are obtained by pressing the seeds to release the oil. The relatively impure oil is filtered, and then purified using an industrial version of a standard laboratory technique. The oil can then be converted to bio-diesel by the reaction with methanol in the presence of a suitable catalyst. (a) (i) Suggest a standard laboratory technique that could be used to purify the oil. (1)(ii) Complete the equation below for the formation of a bio-diesel from the reaction of an oil with methanol. CH2OOCC15H31 3CH3OH + CHOOCC15H31 CH2OOCC15H31 (iii) Suggest a suitable catalyst for the reaction in (a)(ii). (2) (1)22 *P45075A02228*<br />
*(b) Another source of oil currently being investigated for bio-diesel production is the edible plant known as samphire. It can be grown in marshy areas close to coastlines and is tolerant of salt. Consider the advantages and disadvantages of growing both samphire and non-edible seeds as sources of vegetable oil. Suggest, giving your reasons, which of the two sources would provide a potentially greener, more sustainable supply of bio-diesel. (4)(Total for Question 16 = 8 marks) TOTAL FOR SECTION B = 47 MARKS *P45075A02328* 23 Turn over<br />

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$Reject Mark recrystallisa tion Acceptable Answers (fractional) distillation / steam distillation / solvent extraction Ignore filtration /use of separating funnel Acceptable Answers Question Number 16(a)(i) Question Number 16(a) (ii) Mark Mark 3 C15H31COOCH3 Allow 3 CH3OOCC15H31 Allow the correct formulae written three times (1) Correct formula for propane-1,2,3-triol (1) Mark independently Acceptable Answers Sodium hydroxide / potassium hydroxide / NaOH / KOH / OH- Allow sulfuric acid / H2SO4 or other named strong acids or strong alkalis /HCl / just acid / just base / just alkali / just H+ Ignore concentrations of reagents, incorrect or missing state symbols Question Number 16(a) (iii)<br /> Acceptable Answers Do not award any marks for processing the plants or seeds into bio-diesel as the question is about growing Award (1) mark for any statement in the following headings: GREEN e.g. samphire / non-edible seeds / both are renewable / (produce bio-diesel that is) carbon neutral Ignore just green / sustainable LAND e.g. samphire uses land unlikely to be used for growing other food crops / no need to cut down trees to provide land / non-edible seed take up land otherwise used to grow crops WASTE e.g. non-edible seeds have no other use / would be thrown away / can only be used for oil production FOOD e.g. using samphire for bio-diesel reduces availability as a food source FOOD CHAIN e.g. using samphire disrupts the food chain for (marine) organisms GROWING e.g. samphire doesnt need to be irrigated / can take water or nutrients from the marshland Ignore just easier to grow Ignore does not need specific conditions WEATHER e.g. samphire growing is subject to coastal weather TECHNOLOGY e.g. using samphire needs new / improved technology OR machines to farm coastal areas OR higher transport costs (from marshland to production plant) Ignore technology for processing plants or seeds WILL IT WORK? e.g. samphire gives unknown yield / use may need more research To score the maximum of 4 marks, the response must include a decision about which is greener but there is no separate mark for this. Mark Total for Question 16 = 8 marks Question Number 16(b)<br /> Mark Acceptable Answers Ho / kJ mol1 So / J mol1 K1 CH3CH2CH2CH3 O2 CH3CO2H H2O 126.5 484.5 285.8 310.1 205 159.8 69.9 6 values correct 3 marks 4 / 5 values correct 2 marks 2/3 values correct 1 mark 0/1 values correct 0 marks Ignore values multiplied by balancing numbers in addition to correct values eg for water 2 x 285.8 (=571.6) Question Number 17(a) (ii) Mark Acceptable Answers If answer is2256.6 /2257 (kJ mol1), award 2 marks [(2 x 285.8) + (4 x 484.5)](2 x 126.5) (1) =2256.6 /2257 (kJ mol1) (1) Allow answer converted to J mol-1 Allow TE from incorrect data in table in (a)(i) Allow (1) for cycle wrong way round eg (+) 2256.6 / (+)2257 (kJ mol1) Allow (1) for using correct values but not multiplied by balancing numbers eg -643.8 (kJ mol1) Ignore SF except 1SF Section C Question Number 17(a)(i)<br />$

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