Edexcel Jun 2012 Paper 5 Q13 (with explained solutions) |

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Edexcel Jun 2012 Paper 5 Q13

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13 This question is about 1,2-diaminoethane, H2NCH2CH2NH2. (a) Write an equation for the reaction between 1,2-diaminoethane and excess dilute hydrochloric acid. (b) When an aqueous solution of nickel(II) ions is added to 1,2-diaminoethane, a complex ion forms. 3H2NCH2CH2NH2 + Ni(H2O)6 (i) Suggest the colour of this complex. 2+1L +2NCH2CH2NH2)3 2+ + 6H2O (2) (1)(ii) Without using the data booklet, suggest why the complex formed is more stable than Ni(H2O)6 2+ by considering the appropriate entropy change. (2)(iii) This complex can exist as two structures, which are non-superimposable mirror images. Suggest the physical property that would enable you to distinguish between these two structures. (1)12 *P39309A01220*<br />
(c) 1,2-diaminoethane reacts with butane-1,2-dioyl dichloride, ClOCCH2CH2COCl, to form a polymer. (i) Draw a displayed formula for this polymer showing one repeat unit. (ii) Give, and explain, the name for this type of polymerization reaction. (2) (2)*(iii) State and explain the intermolecular forces between two of these polymer chains. (5)(Total for Question 13 = 15 marks) *P39309A01320* 13 Turn over<br />

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$Question Number 13(a) Question Number 13 (b)(i) Acceptable Answers Reject Mark Covalent bond to Cl, (-Cl) + + 2Cl H2NCH2CH2NH2 + 2HCl (cid:74) H3N+CH2CH2NH3 (1) organic product Positive charges can be on nitrogens Balancing with HCl and Cl- (1) Chloride ions can be at ends of product ie ClH3NCH2CH2NH3Cl for right hand side, with or without charges, but if given charges must balance H2NCH2CH2NH2 + 2H+ (cid:74) H3N+CH2CH2NH3 Reaction with 1 mol HCl for 1 max If molecular formulae used 1 max IGNORE state symbols even if wrong + (2) Acceptable Answers Reject Mark Blue or green or blue-green or lavender ALLOW qualification of blue or green e.g. dark blue, but not with another colour e.g. blue purple Any other colour e.g. Purple Violet Acceptable Answers Question Number 13(b)(ii) The entropy change of the system is positive (1) Because there is an increase in the number of particles/entities/moles/molecules OR The number of particles/entities/moles goes from four to seven OR Complex with three molecules goes to a complex with six molecules (1) Second mark depends on a positive entropy change Reject Mark Additional incorrect numbers molecules/ atoms from four to seven<br /> Question Number 13(b)(iii) They will rotate the plane of plane- polarised Acceptable Answers light (equally in opposite directions) Allow They will rotate the plane of polarised light (equally in opposite directions) OR They will rotate plane- polarised light (equally in opposite directions) Acceptable Answers CCH2CH2C CH2CH2 NH NH Question Number 13(c)(i) Reject Mark Optically active Reflect/ bend/ refract Reject Mark Reject Mark Addition/elimination Amide linkage correct (1) Further detail correct, including trailing bonds (1) IGNORE brackets ALLOW multiple units Second mark dependent on correct amide link ALLOW fully correct structural formulae for 1 (OCCH2CH2CONHCH2CH2NH) Can start with NH group Question Number 13(c)(ii) Condensation (1) Acceptable Answers Hydrogen chloride/HCl/water/H2O or another small molecule/is produced/lost/formed/removed (as well as the polymer) (1) Mark independently<br /> Reject Mark Just p.d.- p.d Just v d W Large molecular mass alone Question Number *13(c)(iii) Types of force Acceptable Answers Hydrogen bonds and (permanent) dipole(-permanent dipole) forces and London/van der Waals/dispersion forces OR Explanation e.g temporary/induced dipoles (1) All three needed for 1st mark (which is given even if the forces are later explained incorrectly) Hydrogen bonds (Between) the hydrogen atoms on the nitrogen atoms andOR (Between) N-H and(1)(the lone pair of electrons on) oxygen/ nitrogen atoms (1) These marks can be shown by a diagram Permanent dipole-permanent dipole forces Because the C=O / carbon-oxygen bond/the C-N bond is polar/a dipole OR N and/or O are electronegative atoms This mark can be shown by a diagram providing the polarity of the bond is shown (1) London forces Polymer has large number of/many electrons OR Explanation e.g temporary/induced/fluctuating dipoles (1)<br />$

Question 12 13 14 15

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