CHEMISTRY 5070/21. Published

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1 ambridge International Examinations ambridge Ordinary Level EMISTRY 5070/ Paper Theory May/June 06 MARK SEME Maximum Mark: 75 Published 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. ambridge will not enter into discussions about these mark schemes. ambridge is publishing the mark schemes for the May/June 06 series for most ambridge IGSE, ambridge International A and AS Level components and some ambridge O Level components. IGSE is the registered trademark of ambridge International Examinations. This document consists of 7 printed pages. ULES 06 [Turn over

2 Page Mark Scheme Syllabus Paper ambridge O Level May/June A(a) Poly(propene) () A(b) PV () A(c) Protein () A(d) Starch () A(e) Terylene / polyester () Total: 5 A(a) mark for any one of: Low melting point / low boiling point Does not conduct electricity Does not conduct heat A(b)(i) S + + S / S + + S () A(b)(ii) Incomplete dissociation / partial dissociation () A(c) Moles of S = () Moles of KO = 0.00 / moles of KO = moles of S () 3 A(d)(i) Volume = 66.7 cm 3 () mark each for any two of: igh melting point Does not conduct electricity as a solid Soluble in water onducts electricity as a molten liquid A(d)(ii) Magnesium (atom) loses electrons () Sulfur (atom) gains electrons () Total: 0 ambridge International Examinations 06

3 Page 3 Mark Scheme Syllabus Paper ambridge O Level May/June A3(a) Flavouring () A3(b) O O () A3(c)(i) (Net) movement of a substance from a region of high concentration to low concentration () A3(c)(ii) Rate of diffusion increases () Particles have more energy / particles are moving faster () A3(c)(iii) Methyl methanoate / O 3 () Lowest relative formula mass () Total: 7 A4(a) All three conditions correct ( marks) Two correct conditions ( mark) Temperature: 350 to 500 Pressure: 50 to 000 atmospheres atalyst: iron A4(b) Rate of reaction increases AND particles closer together / more particles per unit volume / more crowded particles () More collisions per second / increased collision frequency / collisions more often () A4(c) Lowers the activation energy () A4(d) Percentage of N in ammonium nitrate = 35% () Percentage of N in urea = 47% () OR Both formulae contain two nitrogen atoms () Urea has a lower relative formula mass () Total: 7 ambridge International Examinations 06

4 Page 4 Mark Scheme Syllabus Paper ambridge O Level May/June A5(a) sodium magnesium X lead silver Sodium, magnesium, lead and silver in correct order (ignore X) () X directly between magnesium and lead () A5(b)(ii) Zinc / iron / tin () A5(c) XO + Mg MgO + X () A5(d) X + Pb + X + + Pb () A5(e) onducts electricity Electrons can move () igh melting point Attraction between sea of electrons and (positive) ions / forces between sea of electrons and ions () Attraction is very strong / force is very strong / it takes a lot of energy to overcome these strong forces () (this mark is dependent on attraction between (positive) ions and electrons / forces between ions and electrons) 3 Total: 8 A6(a)(i) Global warming / ice caps melting / sea level rising () A6(a)(ii) Rotting vegetation () A6(a)(iii) Ozone depletion () A6(b) orrect dot-and-cross diagram for Fl 3 () A6(c)(i) Reaction of nitrogen with oxygen / N + O NO () A6(c)(ii) NO (is reduced) to make N / NO N + O () O (is oxidised) to make O / O + O O () A6(d) NO () Total: 8 ambridge International Examinations 06

5 Page 5 Mark Scheme Syllabus Paper ambridge O Level May/June B7(a) mark each of any four from: 4 Use of excess silver oxide Use of nitric acid Warm the solution / use warm nitric acid / use hot nitric acid Filter mixture to get the solution Evaporate some of the solution and leave / leave to crystallise / warm to crystallisation point / leave on window sill (to crystallise) / evaporate solution then cool B7(b)(i) White precipitate () B7(b)(ii) Ag + (aq) + l (aq) Agl (s) orrect formulae () orrect state symbols dependent on the correct formulae () B7(c)(i) Silver () B7(c)(ii) 4O O + O + 4e () B7(d) 4AgNO 3 Ag O + 4NO + O () Total: 0 B8(a)(i) ontains only carbon-carbon single bonds () B8(a)(ii) ontains only carbon and hydrogen () B8(b) 6 + 9O 6O + 6 O () B8(c) l () 6 l () B8(d) Moles of 6 4 = 3.0 () Mass of 6 = 5 (g) () B8(e)(i) Mole ratio : = 7.4 : 4.3 or 85.7 / and 4.3 / () Divide by 7.4 to get empirical formula () B8(e)(ii) () Total: 0 ambridge International Examinations 06

6 Page 6 Mark Scheme Syllabus Paper ambridge O Level May/June B9(a) Bond breaking absorbs energy and bond making releases energy / bond breaking is endothermic and bond making is exothermic () More energy absorbed than released / less energy released than absorbed / endothermic energy change is more than exothermic energy change / exothermic energy change is less than endothermic energy change () B9(b) Moles of = 0 () B9(c)(i) B9(c)(ii) Energy absorbed = 30 (kj) () Position of equilibrium moves to the left / equilibrium shifts to the reactant side () More moles of gas on product side / fewer moles of gas on reactant side / less volume (of gas) on left (or reverse argument) / fewer molecules of gas on the left ( or reverse argument) () Position of equilibrium moves to the right / equilibrium shifts to the product side () B9(d)(i) B9(d)(ii) Reaction is endothermic / backward reaction is exothermic () Produces carbon monoxide which is toxic or poisonous gas / reaction involves a very high temperature () Saves crude oil / crude oil can be used to make other chemicals / coal or coke is less of a finite resource than crude oil () Total: 0 ambridge International Examinations 06

7 Page 7 Mark Scheme Syllabus Paper ambridge O Level May/June B0(a)(i) Moles of Zn and = 0.0 () Volume of = 0.4 dm 3 () B0(a)(ii) The number of moles of iron is different () B0(b) One mark each for any two observations from: 4 Solution gets warmer / heat given off () White precipitate formed () which redissolves in excess () Green precipitate formed () With excess the green precipitate remains () One mark each for any two explanations from Acid is neutralised () Green precipitate is iron(ii) hydroxide () B0(c)(i) White precipitate of zinc hydroxide () which will redissolve in excess () Oxidation number of iron increases / oxidation number of iron becomes more positive / iron(ii) ions lose electrons () B0(c)(ii) Use (filter paper dipped into acidified) potassium manganate(vii) () Purple colour changes to colourless () Total: 0 ambridge International Examinations 06