MARK SCHEME for the October/November 2012 series 9701 CHEMISTRY

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1 CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 01 series 9701 CHEMISTRY 9701/1 Paper (AS Structured Questions), maximum raw mark 60 This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 01 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

2 Page Mark Scheme Syllabus Paper GCE AS/A LEVEL October/November (a) ZnCO 3 Zn(OH) ZnO not Zn or other compounds of Zn (any ) [] (b) (i) to ensure all of the water of crystallisation had been driven off or to be at constant mass (ii) mass of ZnSO 4 = =.09 g M r ZnSO 4 = (4 16.0) = allow use of Zn = 65 and/or S = 3 to give values between 161 and n(znso 4 ) =.09 = = ZnSO 4 = 161 gives (iii) mass of H O driven off = = 1.63 g n(h O) = 1.63 = = (iv) mol ZnSO 4 are combined with mol H O 1 mol ZnSO 4 is combined with = mol H O answer must be expressed as a whole number allow ecf on candidate s answers to (b)(ii) and (b)(iii) [7] (c) (i) n(zn) = n (CH 3 CO ) Zn.H O n(zn) = = = mass of crystals = = g = 0.05 g = 50 mg (ii) concentration of (CH 3 CO ) Zn.H O = = = mol dm 3 allow correct answers if Zn = 65 is used [4] [Total: 13] Cambridge International Examinations 01

3 Page 3 Mark Scheme Syllabus Paper GCE AS/A LEVEL October/November (a) (i) thermal stability decreases down Group VII (ii) from Cl to I, atomic size increases or the bonding pair is further from the nucleus of X or H X bond becomes longer or smaller orbital overlap occurs hence H X bond strength decreases down Group VII [3] (b) K c = [HI] [H ] [ I ] no units must be clearly stated [] (c) (i) no change K c has no units or same no. of molecules / moles each side of equilibrium (ii) equilibrium moves to RHS K c increases with decreasing temperature or forward reaction is exothermic or reverse reaction is endothermic [4] (d) H (g) + I (g) HI(g) initial moles equil. moles (0.0 y) (0.0 y) y equil. conc/mol dm -3 (0.0 y) (0.0 y) y K c = HI [H ] [ I ] = ( y) (0.0 y) = 59 y = 59 = 77 (0.0 y) y = ( ) 7.7y 9.7y = gives y = at equilibrium = = n(hi) = = 0.03 and n(h ) = n(i ) = ( ) = allow ecf where possible [4] [Total: 13] Cambridge International Examinations 01

4 Page 4 Mark Scheme Syllabus Paper GCE AS/A LEVEL October/November (a) (i) N (g) + 3H (g) NH 3 (g) or N (g) + 3H (g) NH 3 (g) state symbols required (ii) pressure between 60 and 50 atm or between Pa and Pa temperature between 300 and 550 o C catalyst iron / iron oxide (iii) manufacture of HNO 3 / as a cleaning agent / refrigerant / fertiliser / manufacture of fertilisers / explosives / to remove SO from combustion products of hydrocarbon fuels [5] (b) (i) NH 4 Cl and Ca(OH) both formulae required (ii) NH 4 Cl + Ca(OH) CaCl + NH 3 + H O or NH OH NH 3 + H O correct products correctly balanced equation (iii) CaO it is not an acid / it is basic / it does not react with NH 3 or both P O 5 / P 4 O 10 and H SO 4 are acidic / react with NH 3 [5] (c) correct displayed eqn., with positive charge clearly shown lone pair on NH 3 co-ordinate / dative bond clearly shown [3] [Total: 13] Cambridge International Examinations 01

5 Page 5 Mark Scheme Syllabus Paper GCE AS/A LEVEL October/November (a) (i) reaction A B organic compound (CH 3 ) 3 COH CH 3 CH CHO C HCO CH(CH 3 ) reagent Cr O 7 /H + heat under reflux Fehling s reagent warm NaOH(aq) warm structural formulae of organic products no reaction CH 3 CH CO H or CH 3 CH CO HCO Na or HCO (CH 3 ) CHOH D CH =CHCHO NaBH 4 CH =CHCH OH E (CH 3 ) 3 COH NaBH 4 no reaction F CH 3 CH COCH 3 heat under MnO 4 /H + reflux no reaction each correct answer gets (7 1) (ii) reaction colour at the beginning of the reaction colour at the end of the reaction B blue brick red each correct answer gets 1 ( ) [10] (b) (i) (ii) red or orange [] [Total: 1] Cambridge International Examinations 01

6 Page 6 Mark Scheme Syllabus Paper GCE AS/A LEVEL October/November (a) (i) carboxylic acid or alcohol present or carboxylic acid and alcohol present not acid or carboxyl or hydroxyl (ii) carboxylic acid not present or only alcohol present (iii) alkene or >C=C< present [3] (b) (i) each correct structure gets (4 1) (ii) pair 1 geometrical or cis-trans or E/Z isomerism pair optical isomerism accept chiral compounds [6] #1 # [Total: 9] Cambridge International Examinations 01

MARK SCHEME for the October/November 2012 series 9701 CHEMISTRY

CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 202 series 970 CHEMISTRY 970/23 Paper 2 (AS Structured Questions), maximum