Edexcel Jun 2015 (IAL) Paper 1 Q23 (with explained solutions) |

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Edexcel Jun 2015 (IAL) Paper 1 Q23

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23 This question is about alkenes. (a) Give the general formula for the homologous series of alkenes. (1)(b) Give the structural formula of the organic product formed when ethene, CH2=CH2, reacts with (i) hydrogen (ii) chlorine (iii) acidified aqueous potassium manganate(VII) (iv) bromine water (1) (1) (1) (1) 20 *P44880A02028*<br />
(c) When propene, CH3CH=CH2, reacts with hydrogen chloride, there are two possible products, a major product and a minor product. (i) Draw the displayed formulae of these products. Major product Minor product (ii) Give the mechanism for the reaction of propene with hydrogen chloride which forms the major product. (2) (3) *P44880A02128* 21 Turn over<br />
(d) Propene can be polymerized. (i) Write a balanced equation for the polymerization of propene to form poly(propene), drawing the displayed formula of the repeat unit of poly(propene). (ii) State a problem associated with the disposal of waste poly(propene). (3) (1)22 *P44880A02228*<br />
(e) Standard enthalpy changes of combustion can be used to calculate the standard enthalpy change of formation of propene. 3C(s) + 3H2(g) C3H6(g) Values for some standard enthalpy changes of combustion, (cid:507)H (cid:57) table below. c , are shown in the Substance (cid:507)H (cid:57) c / kJ mol1 C(s) H2(g) C3H6(g) 394 286 2058 (i) Complete the Hess cycle below to enable you to calculate (cid:507)H f (cid:57) from combustion data. 3C(s) + 3H2(g) (cid:57) (cid:507)H f C3H6(g) (ii) Calculate (cid:507)H f (cid:57), in kJ mol1. (1) (2) standard enthalpy change of formation of propene =kJ mol1 (Total for Question 23 = 17 marks) *P44880A02328* 23 Turn over<br />

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Question Number 23(a) Acceptable Answers CnH2n ALLOW Letters other than n ALLOW: (partially) displayed or skeletal formulae throughout Q23(b) IGNORE: additional incorrect non-organic products Question Number 23(b)(i) CH3CH3 Acceptable Answers Reject Question Number 23(b)(ii) ClCH2CH2Cl / CH2ClCH2Cl Acceptable Answers Reject C2H6 Reject C2H4Cl2 Mark Mark Mark ONLY PENALISE ONCE ONLY in (b)(iii) & (b)(iv) THE CONNECTIVITY BETWEEN C and OH if CLEARLY a C to H covalent bond has been drawn Question Number 23(b)(iii) HOCH2CH2OH / CH2OHCH2OH Acceptable Answers Reject Mark C2H6O2 / OHCH2CH2OH Question Number 23(b)(iv) HOCH2CH2Br / CH2OHCH2Br Acceptable Answers Reject BrCH2CH2Br / C2H5OBr / C2H4Br2 Mark<br />
PENALISE USE OF Br instead of Cl once only in parts (c)(i) & (c)(ii) PENALISE missing H atoms from displayed formulae once only in parts (c)(i) & (c)(ii) Question Number 23(c)(i) Acceptable Answers Reject Cl Mark (Major product) (1) Cl (Minor product) (1) Both DISPLAYED structures, with all bonds and atoms shown but in the wrong boxes scores (1) PENALISE CH3 not fully displayed ONCE only So CH3CH(Cl)CH3 and CH3CH2CH2Cl scores (1)<br />
Acceptable Answers Reject Mark H3C Cl both arrows (1) H3C (:)Cl H3C + Cl carbocation (1) H3C Cl attack of chloride ion (1) 1st mark: Curly arrow from C=C to H (in HCl) AND curly arrow from bond in HCl to the Cl (dipole not reqd) Curly arrows must start from the bonds NOT the atoms (1) 2nd mark: Structure of correct secondary carbocation (1) 3rd mark: Curly arrow from anywhere on the chloride ion (including the minus sign) towards the C+ on the carbocation (1) NOTE: The chloride ion must have a full negative charge, but the lone pair of electrons on the Cl need not be shown ALLOW: TE on major product given in (c)(i) Skeletal formulae can be used Mark the three points independently Full + andcharges on HCl Incorrect polarity on HCl Extra / spare bond dangling from the C+ carbon - on chloride ion instead of Cl Question Number 23(c)(ii)<br />
Acceptable Answers nC3H6TWO n in the equation and a correct formula (molecular or structural) for propene on the left-hand side of the equation (1) Reject Mark One correct repeating unit, with the methyl branch shown (1) ALLOW CH3 fully displayed or just as CH3 BOTH continuation bonds (with or without bracket shown) (1) If C=C bond left in polymer on right- hand side, then max (1) Mark the three points independently Question Number 23(d)(i)<br />
Reject Mark IGNORE References to toxicity of poly(propene) / flammability IGNORE Litter / pollution / waste of resources / costs ALLOW People are reluctant to recycle OR Harmful to marine life / harmful to wildlife OR References to landfill OR References to incineration producing toxic fumes/toxic gases / CO2 / Greenhouse gases OR References to use of energy/fuel used in transport (of waste) OR It takes a long time to degrade Question Number 23(d)(ii) Non-biodegradable Acceptable Answers<br />
Question Number 23(e)(i) Acceptable Answers Hf C3H6(g) 3CO2(g) and 3H2O(l) 3C(s) + 3H2(g) (+4O2) (+4O2) Both arrows in the correct direction AND 3CO2 and 3H2O in lowest box IGNORE state symbols, even if incorrect IGNORE extra O2 molecules in box or alongside arrows Acceptable Answers Question Number 23(e)(ii) 1st mark Reject Mark Reject Mark (394 x 3) + (286 x 3) OR = 2040 (kJ mol1) (1) 2nd mark: Hf = 2040(2058) = (+)18 (kJ mol1) (1) NOTE: The following answers score (1) mark with or without working 18 (kJ mol1) (+)1378 (kJ mol1) (+)806 (kJ mol1) (+)590 (kJ mol1) 4098 (kJ mol1) IGNORE units even if incorrect (Total for Question 23 = 17 marks<br />

Question 17 18 19 20 21 22 23 24

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