Edexcel Jun 2013 Paper 1 Q22 (with explained solutions) |

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Edexcel Jun 2013 Paper 1 Q22

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22 This question is about ethene and its reactions. Ethene is produced in industry by cracking. (a) (i) Write the equation for the cracking of dodecane, C12H26, to produce one mole of ethene as the only alkene product. (ii) Draw a labelled diagram of the apparatus and materials you would use to crack dodecane and collect a sample of the gaseous alkene in the laboratory. (1) (4) *P41649A02124* 21 Turn over<br />
(b) Draw a diagram to show the regions of electron density in both parts of the double bond between the carbon atoms in ethene. Label each region with appropriate symbols. (c) (i) Give the name and structural formula for the product of the reaction between ethene and bromine, Br2(l). NameFormula (ii) Give the mechanism for the reaction between ethene and bromine. (2) (2) (3) 22 *P41649A02224*<br />
(d) Give the displayed formula for the organic product of the reaction between ethene and acidified potassium manganate(VII). (e) (i) Write a balanced equation for the formation of poly(ethene) from ethene, showing the structure of the polymer clearly. (ii) Comment on the atom economy of the reaction in (e)(i). (1) (2) (1)(Total for Question 22 = 16 marks) TOTAL FOR SECTION B = 60 MARKS TOTAL FOR PAPER = 80 MARKS *P41649A02324* 23<br />

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Question Number 22(a)(i) C12H26 C10H22 + C2H4 Acceptable Answers Reject IGNORE state symbols even if incorrect ALLOW displayed and structural formula for ethene Question Number 22 (a)(ii) Acceptable Answers Reject Delivery tube through glassware Collection over water or in gas syringe (1) IGNORE solid bung with delivery tube coming out / accidental sealing in drawing / clamps This is the only stand alone mark Dependent on diagram including roughly horizontal tube: Labelled ceramic fibre / any sort of wool (unless any named metal) (soaked in dodecane) (1) Aluminium oxide / porcelain pieces/catalyst / catalyst with incorrect name or incorrect formula / any named metal / anti-bump granules (1) Heat under catalyst/under middle of test tube (1) Mark Mark<br />
Questio n Number 22(b) Acceptable Answers Reject Mark EITHER Diagram of bonds, the single bond must be shown as a region of space and not as a single or double straight line (1) Labelledandin correct places on correctly drawn bonds.ie this mark can only be awarded if bonds correctly drawn (1) OR Labelled pi bond (1) Labelled sigma bond (1) Whichever scores more Bonds may be shown by overlap of appropriate orbitals, when any orbital or region of overlap may be labelled Only one pi lobe / bond need be labelled Carbons need not be shown Bonds may be drawn on separate diagrams<br />
IGNORE C-H bonds IGNORE any additional electron density maps IGNORE any partial charges Question Number 22(c)(i) 1,2-dibromoethane (1) Acceptable Answers IGNORE punctuation CH2BrCH2Br (1) ALLOW displayed / skeletal formula Mark independently Bromoethane with CH2BrCH3 (0) Acceptable Answers Question Number 22 (c)(ii) Arrow from double bond towards nearest bromine atom and arrow from bond between bromine atoms to furthest bromine atom (1) Correct formula of carbocation intermediate (1) Arrow from anywhere on the bromide ion to positive carbon (1) ALLOW missing hydrogens if bonds from carbons shown ALLOW full marks for TE bromoethane formation using HBr and first arrow to H of HBr ALLOW full marks for TE 1,2dibromopropane Mark Reject C2H4Br2 Reject Mark<br />
Question Number 22(d) Acceptable Answers ALLOW O-H not displayed ALLOW vertical C bond to any part of OH Only penalise clear C-H-O / CH-O bond horizontally IGNORE any name whether correct or not Acceptable Answers nCH2=CH2(CH2-CH2)n Left side (1) Right side extension bonds must be shown (1) Mark independently Accept nC2H4(CH2-CH2)n Penalise omission of n only once ALLOW nCH2=CH2 + nCH2=CH2(CH2-CH2)n for (2) ALLOW multiples of C2H4 in product Question Number 22(e)(i) Mark Reject Skeletal formula or structural formula Mark Reject (CH2=CH2 )n N<br />
Question Number 22(e)(ii) 100% with one of the following: Acceptable Answers only one product ORno by-products / no other product OR all reactants form the product OR as addition reaction IGNOREsame empirical formula Mark Reject No product lost / No side reaction(s) All reactants form the products Total for Question 22 = 16 Marks Total for Paper = 80 Marks<br />

Question 18 19 20 21 22 23 24 25

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