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CIE Nov 2015 v1 Paper 2 Q3
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![Heptane, C7H16, is an undesirable component of petrol as it burns explosively causing knocking in an engine. PMT (a) There are nine structural isomers with the formula C7H16, only two of which contain chiral centres. (i) Explain the meanings of the terms structural isomers and chiral. structural isomerschiral[2] (ii) Give the structures and names of the two structural isomers of C7H16 which contain a chiral centre. [4] (b) (i) Write an equation for the complete combustion of heptane.[1] (ii) Write an equation for the incomplete combustion of heptane leading to the production of a solid pollutant.[1] (iii) Incomplete combustion can also lead to emission of unburnt hydrocarbons. State one environmental consequence of this.[1]UCLES 2015 9701/21/O/N/15<br />
PMT (c) The reaction of heptane with chlorine in the presence of UV light produces a wide variety of products. Formation of the monochloroheptanes can be represented by the following equation. C7H16 + Cl 2C7H15Cl + HCl (i) Name the mechanism of the reaction between heptane and chlorine in the presence of UV light.[1] (ii) Describe this mechanism, using suitable equations and including the names of each stage in the process.[5]UCLES 2015 9701/21/O/N/15 [Total: 15] [Turn over<br />](https://learnah.org/wp-content/uploads/2018/08/November_2015_v1_QP_-_Paper_2_CIE_Chemistry_A-level_3-0.jpg)
![Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A LevelOctober/November 2015 9701 21 Question Mark Scheme (c) (i) 2NH3 + H3PO4(NH4)2HPO4 (ii) NH3 identified as base AND H3PO4 identified as acid base accepts protons AND acid donates protons (d) (i) nitrates / fertilisers wash into rivers eutrophication / algal bloom / promote algal growth bacteria use up oxygen in decay process (ii) (oxides of nitrogen / NOx / NOs) cause acid rain 2NO2 + H2OHNO2 + HNO3 OR 4NO2 + 2H2O + O24HNO3 OR SO2 + NO2SO3 + NO AND SO3 + H2OH2SO4 PMT Mark Total [1] [1] [1] [1] [1] [1] [1] [1] [1] [2] [3] [2] [21] (a) (i) structural isomers: (different molecules with) same molecular formula but different structural formulae chiral: has a carbon / C attached to 4 different groups / atoms / chains OR has no plane / line of symmetry / has non-superimposable mirror images (ii) CH3CH2CH(CH3)CH2CH2CH3 3-methylhexane CH3CH(CH3)CH(CH3)CH2CH3 2,3-dimethylpentane / (CH3)2CHCH(CH3)CH2CH3 (b) (i) C7H16 + 11O27CO2 + 8H2O (ii) C7H16 + 4O27C + 8H2OCambridge International Examinations 2015 [1] [1] [1] [1] [1] [1] [2] [4] [1] [1] [1] [1]<br />
Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A LevelOctober/November 2015 9701 21 Question Mark Scheme (iii) global dimming / PAN / smog / global warming (c) (i) (Free) Radical Substitution (ii) Cl 22Cl OR Cl 2Cl + Cl C7H16 + ClC7H15 + HCl C7H15 + Cl 2C7H15Cl + Cl C7H15 + ClC7H15Cl OR C7H15 + C7H15C14H30 Initiation; Propagation; Termination (used correctly) PMT Mark Total [1] [1] [1] [1] [1] [1] [1] [1] [1] [5] [15] (a) (i) CH3CH2OH + HClCH3CH2Cl + H2O or CH3CH2OH + PCl 5CH3CH2Cl + HCl + POCl [1+1] [2] or CH3CH2OH + SOCl 2CH3CH2Cl + HCl + SO2 (ii) NaOH / KOH warm / heat / reflux AND aqueous (b) (i) CH2=CH2 / ethane / C2H4 / CH2CH2 (ii) White ppt / solid / suspension (iii) Ag (aq) + Cl (aq)AgCl (s) (c) (i) CH3CHO / ethanalCambridge International Examinations 2015 [1] [1] [2] [1] [1] [1] [1] [1] [1] [1] [1]<br />](https://learnah.org/wp-content/uploads/2018/08/November_2015_v1_MS_-_Paper_2_CIE_Chemistry_A-level_3-0.jpg)
