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CIE Nov 2013 v2 Paper 4 Q4
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![Examiners For Use (a) Explain what is meant by the term bond energy.[2] (b) (i) Describe and explain the trend in bond energies of the CX bond in halogenoalkanes, where X = F, Cl, Br or I.(ii) Describe the relationship between the reactivity of halogenoalkanes, RX, and the bond energies of the CX bond.[3] (c) Use the Data Booklet to suggest an explanation as to why CFCs such as CF2Cl 2 are much more harmful to the ozone layer thanuorocarbons such as CF4 or hydrocarbons such as butane, C4H10.[3] (d) Predict the products of the following reactions and draw their structures in the boxes below. The molecular formula of each product is given, where X = Cl , Br or I. Cl Cl Br H2O H2O H2O Cl Br C3H5O2X C3H7OX C7H7OX [3]UCLES 2013 9701/42/O/N/13<br />
Examiners For Use (e) Ethane reacts with chlorine according to the following equation. C2H6 + Cl 2C2H5Cl + HCl (i) State the conditions needed for this reaction.(ii) State the type of reaction occurring here.One of the steps during this reaction is the following process. Cl+ CH3CH3HCl + CH3CH2 (iii) Use the Data Booklet to calculate the enthalpy change, H, of this step. (iv) Use the Data Booklet to calculate the enthalpy change, H, of the similar reaction: I + CH3CH3HI + CH3CH2 H =kJ mol1 H =kJ mol1 (v) Hence suggest why it is not possible to make iodoethane by reacting together iodine and ethane.(vi) Complete the following equations of some possible steps in the formation of chloroethane. Cl 2Cl+ CH3CH3HCl + CH3CH2 CH3CH2+++CH3CH2Cl [8] [Total: 19]UCLES 2013 9701/42/O/N/13 [Turn over<br />](https://learnah.org/wp-content/uploads/2018/08/November_2013_v2_QP_-_Paper_4_CIE_Chemistry_A-level_4-0.jpg)
![Page 5 Mark Scheme Syllabus Paper GCE A LEVELOctober/November 2013 9701 42 (a) (the energy change) when 1 mol of bonds is broken in the gas phase (b) (i) (C-X bond energy) decreases/becomes weaker (from F to I) due to bond becoming longer/not such efficient orbital overlap (ii) (as the bond energy of C-X decreases) the halogenalkanes become more reactive (answer must imply that it is from F to I) (c) The C-Cl bond is weaker than the C-F and C-H bonds or C-Cl bond (E = 340) and C-H (E = 410) so is (easily) broken to form Cl/Cl radicals/Cl atoms causing the breakdown of O3 into O2 (d) Cl-CH2CH2-CO2H HO-CH2CH2CH2-Cl OH Br (e) (i) light/UV/h or 300C [1] [1] [2] [1] [1] [1] [3] [1] [1] [1] [3] [1] [1] [1] [3] [1] [1] [1] (ii) (free) radical substitution (iii) H = E(C-H)E(H-Cl) = 410431 = 21 kJ mol (iv) H = E(C-H)E(H-I) = 410299 = +111 kJ mol (v) The reaction with iodine is endothermic or H is positive or requires energy (vi) Cl 22Cl+ Cl + ClCH3CH2 CH 3CH2 2CH3CH2Cl + ClCH3CH2ClCambridge International Examinations 2013 ecf [1] [1] [1] [1] [1] [8] [Total: 19]<br />](https://learnah.org/wp-content/uploads/2018/08/November_2013_v2_MS_-_Paper_4_CIE_Chemistry_A-level_4.jpg)