Edexcel Jan 2012 Paper 1 Q25 (with explained solutions) |

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Edexcel Jan 2012 Paper 1 Q25

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25 Chloroethane can be made from ethane and chlorine in the gas phase in the presence of ultraviolet light. The equation for the reaction is CH3CH3 + Cl2(cid:3)(cid:111)(cid:3)CH3CH2Cl + HCl PMT (a) Complete the mechanism for the reaction. Two of the steps have been given for you. (4) Initiation: Propagation (two steps) Cl2(cid:3)(cid:111)(cid:3)2Cl (i) (ii) Termination (three steps) 2Cl(cid:3)(cid:111)(cid:3)Cl2 (iii) (iv) (b) This reaction gives a poor yield of chloroethane. Give the structural formula and name of another organic product, not included in your mechanism for part (a), which could be produced in the reaction. (2) Formula Name*P39295A02124* 21 Turn over<br />
(c) Chlorine gas is extremely toxic and is therefore a significant hazard. The preparation (cid:80)(cid:88)(cid:86)(cid:87)(cid:3)(cid:69)(cid:72)(cid:3)(cid:83)(cid:72)(cid:85)(cid:73)(cid:82)(cid:85)(cid:80)(cid:72)(cid:71)(cid:3)(cid:86)(cid:82)(cid:3)(cid:68)(cid:86)(cid:3)(cid:87)(cid:82)(cid:3)(cid:80)(cid:76)(cid:81)(cid:76)(cid:80)(cid:76)(cid:86)(cid:72)(cid:3)(cid:87)(cid:75)(cid:72)(cid:3)(cid:85)(cid:76)(cid:86)(cid:78)(cid:3)(cid:87)(cid:82)(cid:3)(cid:87)(cid:75)(cid:72)(cid:3)(cid:72)(cid:91)(cid:83)(cid:72)(cid:85)(cid:76)(cid:80)(cid:72)(cid:81)(cid:87)(cid:72)(cid:85)(cid:17) (i) Explain the difference between hazard and risk. PMT (2)(cid:3) (cid:3) (cid:11)(cid:76)(cid:76)(cid:12)(cid:3) (cid:42)(cid:76)(cid:89)(cid:72)(cid:3)(cid:82)(cid:81)(cid:72)(cid:3)(cid:83)(cid:85)(cid:72)(cid:70)(cid:68)(cid:88)(cid:87)(cid:76)(cid:82)(cid:81)(cid:3)(cid:87)(cid:75)(cid:68)(cid:87)(cid:3)(cid:92)(cid:82)(cid:88)(cid:3)(cid:90)(cid:82)(cid:88)(cid:79)(cid:71)(cid:3)(cid:88)(cid:86)(cid:72)(cid:3)(cid:76)(cid:81)(cid:3)(cid:87)(cid:75)(cid:76)(cid:86)(cid:3)(cid:72)(cid:91)(cid:83)(cid:72)(cid:85)(cid:76)(cid:80)(cid:72)(cid:81)(cid:87)(cid:3)(cid:87)(cid:82)(cid:3)(cid:80)(cid:76)(cid:81)(cid:76)(cid:80)(cid:76)(cid:86)(cid:72)(cid:3)(cid:87)(cid:75)(cid:72)(cid:3)(cid:85)(cid:76)(cid:86)(cid:78)(cid:15)(cid:3) other than the use of a laboratory coat and safety goggles. (1)(Total for Question 25 = 9 marks) 22 *P39295A02224*<br />

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N.B. Throughout, ALLOW C2H6 for CH3CH3 and C2H5Cl for CH3CH2Cl and C2H5 for CH3CH2 and C4H10 for CH3CH2CH2CH3 etc If CH4 used instead of CH3CH3 max (1) mark overall for (a)(i) and (a)(ii) taken together Then mark (a)(iii) and (a)(iv) CQ as for CH4 IGNORE positions of the dots in free radicals; dots must be shown in each radical Acceptable Answers Question Number 25(a)(i) CH3CH3 + ClCH3CH2+ HCl Reject OR CH3CH2+ Cl2CH3CH2Cl + Cl Acceptable Answers Question Number 25(a)(ii) CH3CH2+ Cl2CH3CH2Cl + Cl Reject OR CH3CH3 + ClCH3CH2+ HCl N.B. different answers for (i) and (ii) needed Mark Mark Acceptable Answers Question Number 25(a)(iii) 2CH3CH2CH3CH2CH2CH3 Reject Mark Cl + ClCl2 OR CH3CH2+ ClCH3CH2Cl Acceptable Answers Question Number 25(a)(iv) CH3CH2+ ClCH3CH2Cl Reject Mark OR 2CH3CH2CH3CH2CH2CH3 N.B. different answers for (iii) and (iv) needed 6CH0101 1201<br />
Question Number 25(b) Mark Acceptable Answers Reject Butane /C4H10 / CH3CH2CH2CH3 / chlorobutane / hexane / chloromethane First mark: Structural formula (enough to see the structure) of any polyhalogenated ethane derivative OR any polyhalogenated methane derivative ALLOW correct displayed or skeletal formula (1) Second mark: If first mark awarded the name must be consequentially correct IGNORE any missing or incorrect numbering in name (e.g. dichloroethane scores the mark) IGNORE missing or incorrect hyphens If first mark NOT awarded then only ALLOW correct name of any polyhalogenated ethane or polyhalogenated methane derivative (1) 6CH0101 1201<br />
Acceptable Answers Question Number 25(c)(i) 1st mark for HAZARD: Reject Mark Just causes harm/just is a danger Mark This mark is for the idea of: (substance or procedure that) can cause harm/may cause harm/has the potential to do harm/can be dangerous ALLOW references to specific hazards such as toxic/flammable /harmful/ irritant /corrosive /oxidizing/ carcinogenic for the mark (1) 2nd mark for RISK: This mark is for the idea of likelihood/probability/chance that harm will result (from the use of a substance or a procedure) (1) Question Number 25(c)(ii) Acceptable Answers Reject fume cupboard OR gloves OR u.v. goggles Just open windows/Just well-ventilated lab/Just gas mask/Just use of smaller quantities/close d system/closed experiment 6CH0101 1201<br />

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