M1. (a) Mendeleev 1. atomic weight 1. undiscovered 1. electronic structures 1 [5] (b) (i) A 1

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1 M. (a) Mendeleev atomic weight (c) groups (d) undiscovered (e) electronic structures [5] M. (a) sodium is a metal sodium forms ions with a + charge (i) A B (iii) hydrogen [5] M3. (a) (i) argon and potassium or tellurium and iodine or cobalt and nickel accept correct symbols allow argon and calcium it would place them in incorrect groups (owtte) idea of not being placed with elements which have similar properties or converse argument accept would not have same number of electrons in outer shell allow it would put them in wrong period if linked to argon and potassium / calcium do not accept reasons based just on protons do not accept metals and non-metals mixed up Page of 3

2 any two from: each successive atom has one more electron atoms in the same group have the same number of electrons in their outer shells / energy levels number of electrons in outer shell = group number across a period an energy level / shell is being filled in the next period the next energy level / shell is being filled accept period number = shell number [4] M4. (i) any two sensible ideas such as: (why) put in order of mass accept other equally valid orders, eg alphabetical he left gaps or table not complete no evidence for undiscovered elements or they believed all the elements had been discovered accept predictions could not be backed by evidence accept why change previous ideas he changed the order of some elements or there were exceptions to the rule(s) he put metals and non-metals together accept they didn t like his groupings / groups he did not explain his ideas clearly (owtte) do not accept modern explanations, eg proton number etc (the properties of gallium) fitted the predictions (owtte) or predictions were correct or (properties) would make it fit in the gap or (properties) would make it fit in group 3 do not accept gallium fitted his theory accept finding gallium proved there were new elements to be discovered [3] M5. (a) Mendeleev arranged known elements in order of mass or properties reject explanation in terms of electrons and / or atomic number gaps in Periodic Table / group Page of 3

3 does not last long enough to experiment / very little of it allow it has a short half-life (c) (i) (much) more violent accept more reactive since outer electron / or shell further from nucleus do not credit lower down group larger / more shells neutral therefore more easily lost accept screening by inner electrons [6] M6. (a) A is sodium/na* B is argon/ar* each for mark (*case of letters must be correct) (i) ideas that outer electron (in element C /.8.8. / potassium) is at a higher energy level / in a more outer shell/further away from nucleus / shielded by more full electron shells electron is more easily lost/less strongly held / attracted each for mark ideas that (element B /.8.8 / argon) has an outer shell that is complete/has 8 electrons no tendency to gain or lose electrons / has a stable configuration (not is stable / in group O / a noble gas ) each for mark [6] M7. (a) same number of outer electrons / have outer electrons do not accept inner electrons or Xs Page 3 of 3

4 calcium (idea) outer electrons / shell further from nucleus do not credit lower down group do not credit larger / more shells more easily lost / attraction from nucleus less accept screening of inner electrons [3] M8. (a) acts as barrier between sodium and air / oxygen / water (vapour) accept because they are reactive ignore oil will not react Na + H O NaOH + H allow multiples / fractions (c) these metals react with water producing an alkaline solution or produce solution with ph greater than 7 / high ph owtte allow produce OH. ions not these metals are / form alkalis ignore strong ph Page 4 of 3

5 (d) it = potassium outer electron must be mentioned once for all 3 marks bigger atom or outer shell electron further from nucleus or more shells or converse argument for sodium less reactive provided sodium is specified less attraction to nucleus or more shielding not less magnetic attraction outer electron more easily lost ignore potassium reacts more easily [6] M9. (a) group seven/7vii accept halogens (i) in light bulbs/lasers accept any other specified use as an inert atmosphere e.g. (argon) welding, storing explosives, fluorescent lights.8.8/has a full/8 in/outer shell electrons accept does not need to share/gain/lose electrons (c) (i) any one from: disinfectant bleaching agent sterilising water/kills bacteria manufacture of HCl water treatment Page 5 of 3

6 not: cleaning/in pools purification of water kills germs warfare antiseptic inner shells,8 outer shell 7 (iii) fluorine: accept the converse reasons for chlorine gains one/an electron easier/is more strongly attracted not more strongly held less shielding of nucleus by inner electron shells less distance from (attraction of) nucleus/less shells [0] M0. (a) (i) iodine fluorine or chlorine (iii),7 (iv) astatine (i) chlorine>bromine>iodine Page 6 of 3

7 any two suitable comparisons about the extent to which the iron wool glowed eg chlorine is more reactive than bromine because iron glowed more brightly with chlorine than bromine () eg bromine is more reactive than iodine because iron glowed with bromine but not with iodine () [7] M. (a) water (allow acid*) (metal) hydroxide (solution)/alkali (allow metal salt / compound) hydrogen (allow hydrogen) for mark each (*if named acid then matching salt) or oxygen / chlorine / halogen for mark oxide / chloride / halide gains mark but named oxide(s) gains marks (accept fully correct formulae throughout) 3 idea that hydrogen and iodine would only react if heated to > 00 C / a high temperature (ignore reference to light / dark) reactivity decreases down the Group / iodine is lower in the Group than bromine / iodine is the lowest in the Group (or converse N.B. credit this idea here even if given in (d)) for mark each (c) H + Cl HCl or ½H + ½ Cl HCl for mark Page 7 of 3

8 (d) idea that (or converse) in atoms lower down the Group the electrons in the outer shell / highest energy level (of electrons) are further from the nucleus or shielded by more (inner) shells / electrons [but not simply more electrons ] or are less strongly attracted to the nucleus so an electron is less easily gained for mark each [8] M. (a) potassium / it is an alkali metal or it is in group or it is reactive it = potassium allow argon is a noble gas / unreactive / group 0 ignore references to atomic structure ignore references to correct physical properties group 4 / they are metals and non-metals accept element missing or gap left ignore differences in properties (c) it / they fitted at the beginning / end of the table ignore left gaps / spaces [3] M3. (a) B eg link between Li, Na, K, (Rb, Cs) or Mg, Ca, (Sr, Ba) or F, Cl, Br, I allow any two elements in the same group (in both Newland s and the modern periodic table) linked appropriate comment about that link eg similar physical / chemical properties or similar specific reactions or same number of outer electrons if no elements identified, allow mark for a general comment about elements in the same column having similar properties every eighth element has similar properties = mark Page 8 of 3

9 (c) any two from: no gaps for undiscovered elements or elements still being discovered some boxes have elements metals and non-metals in same column / mixed up / some elements in the same column had different properties pattern for first 6 or so elements only any sensible suggestion about misplaced elements eg copper in group metals (d) alkanes are not elements or alkanes are compounds ignore molecule / molecular [6] M4. (a) acidic } neutral } in this order alkaline} all correct marks one correct mark ideas that nothing happens at first (to ph) / ph stays the same then (rapidly) changes / increases then stays at same (higher) level 5 [7] M5. (a) kills bacteria / sterilises (water) allow kills microorganisms / microbes / germs allow makes (water) safe (to drink) or disinfectant ignore cleans water or removes impurities / bacteria goes colourless / decolourised (from red / red-brown / brown / yellow / orange) allow colour disappears ignore goes clear or discoloured do not accept incorrect initial colour do not accept precipitate Page 9 of 3

10 (c) (i) Br and Cl allow multiples / fractions if whole equation balanced changes to red / red-brown / brown / yellow / orange do not accept effervescence / fizzing / precipitate / gas given off ignore vapour / temperature changes / ignore initial colour (d) (i) 7 outer electrons or same number of outer electrons allow last / final shell for outer allow energy level / orbit / ring for shell allow need to gain e to have a full outer shell ignore similar number of outer electrons bromine / it (atom) is bigger or must be a comparison outer electrons (level / shell) further from nucleus or more shells do not accept more outer shells ignore more electrons forces / attractions are weaker or more shielding or attracts less do not accept magnetic / gravitational / intermolecular forces allow electron(s) attracted less easily electron(s) gained less easily outer / last / final must be mentioned once, otherwise max marks. accept converse for chlorine throughout where clearly stated 3 (e) (i) white precipitate or white solid ignore names of chemicals cream precipitate or cream solid allow pale yellow / off-white precipitate / solid ignore names of chemicals [0] M6. (a) (i) burette conical flask accept conical / flask Page 0 of 3

11 (i) an indicator (iii) changed colour titration (c) 3 correct answer = marks ( 3) or ( 750/50) = mark (d) (i) hydrogen is partially ionised [9] M7. (a) any four from: sulphuric acid measure by pipette or diagram potassium hydroxide in burette or diagram if solutions reversed, award note initial reading use of indicator note final reading or amount used 4 = Page of 3

12 (c) ½ or 0.5 moles H SO 4 react with mole KOH moles H SO 4 in 5.0 cm 3 = moles H SO 4 in dm 3 = =.36 mol/dm 3 [9] M8. (a) calcium carbonate allow formulae (i) soap allow marks for contains CaSO 4 / Ca(HCO 3 ) / Ca + / Mg + forms scum / no bubbles / no lather allow mark for contains Ca / Mg do not allow contains CaCO 3 taste / strengthen bones, teeth etc / health reason e.g. less heart disease / makes better beer (c) (shake with) soap; makes scum / no lather boil (a fresh sample) retest with soap result/comparison alternative answers: boil (not to dryness) cloudiness in water/some deposit formed if a comparison is made with a sample of a soft water, a further marks would be possible Page of 3

13 (d) ion-exchange [0] M9. (i) calcium (ion) / Ca + ignore any formula if ion only must be correct accept magnesium (ion) / Mg + do not accept named compounds contact with rocks accept named rocks ignore ground / deposits / soil / minerals / ores (ions / substances) dissolved / soluble / leached / reacts ignore erode / corrode / picks up / absorb (iii) (ions / substances / they) react / replace / remove accept displace forms precipitate / insoluble / solid if ion exchange (column) = max mark [5] M0. (a) (i) dissolve calcium (i) easily makes lather with soap soft water made soft by boiling temporary hard water (c) filter add chlorine accept sterilise [6] Page 3 of 3

14 M. (a) must be description of a titration no titration = no marks NaOH in burette do not accept biuret etc add NaOH until (indicator) changes colour if specific colour change mentioned, must be correct colourless to pink / red or goes pink / red do not accept clear for colourless note (burette) volume used or final reading accept work out the volume one other point: eg repeat accept: (white) tile or add dropwise / slowly or white background or swirling / mix or read meniscus at eye level or wash apparatus for marks (0. 3.5)/5 for mark (c) don t know insufficient evidence to decide owtte any sensible answer or depends on whether acid level is considered safe or unsafe yes, safe acid level low / weak acids / low compared with stomach acid owtte any sensible answer no, unsafe acid level (too) high / other substances or bacteria may be present / insufficient evidence to decide owtte any sensible answer (d) (methyl orange) would have changed colour (well) before the end-point / ph7 / neutral owtte weak acid present weak acid-strong base (titration) allow methyl orange used for strong acid-weak base titration [9] Page 4 of 3

15 M. (a) must be a description of a titration no titration = 0 marks Quality of written communication for correct sequencing of of first 3 bullet points i.e. + or + 3 or + 3 any three from: nitric acid in burette do not accept biuret can be inferred from 3rd point add nitric acid until indicator changes (colour) can be named acid-base indicator colour change does not have to be correct note (burette) volume used or final reading accuracy: e.g. repeat accept white tile or dropwise near end or white background or swirling the flask or read meniscus at eye level 3 e.g. formula method: 5 M NH3 = M NH3 = 0. correct answer alone = OR moles NH 3 = moles HNO 3 = 0.5 = moles () concentration NH3 = = 0. () Page 5 of 3

16 (c) sodium hydroxide or potassium hydroxide or lithium hydroxide or calcium hydroxide ignore mention of alkali ammonia produced accept gas produced turns (damp) (red) litmus blue (not blue litmus) or alkaline gas produced any suitable named indicator e.g. UI with consequential marking white fumes / smoke with (concentrated) HCl do not accept white gas wrong test = 0 marks [8] M3. (a) (i) on heating, the calcium hydrogencarbonate decomposes forming a scale of insoluble calcium carbonate the scale reduces the efficiency of the heating element or the scale increases energy costs / uses more energy (i) the sodium carbonate / carbonate ions react with calcium / magnesium ions, forming a precipitate of calcium carbonate / magnesium carbonate therefore the water is softened because this removes the calcium / magnesium ions, which cause hardness, from the water sodium / hydrogen ions are present in the ion exchange resin therefore the water is softened because these ions take the place of calcium / magnesium ions that cause hardness in the water [7] M4. (a) Drain Buster is a concentrated sodium hydroxide solution that would damage the skin therefore it is diluted so that it is safe to use for the experiment Page 6 of 3

17 Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response. No relevant content. There is a brief description of the titration that may include a risk assessment. There is some description of the titration that may include a risk assessment. There is a clear, balanced and detailed description of the titration and an appropriate risk assessment. 0 marks Level ( marks) Level (3 4 marks) Level 3 (5 6 marks) examples of the chemistry points made in the response burette / acid / HCl used correctly pipette used for Drain Buster solution / alkali / NaOH correctly read meniscus at eye level acid / HCl added dropwise indicator used white background/tile end-point of titration recorded swirling/mixing repeat example of risk assessment points made in the response eg Wear safety goggles to protect eyes because hydrochloric acid is corrosive / irritant and / or sodium hydroxide is caustic [8] M5. (a) (i) both scales (must be sensible) (use at least half the paper ) plots for 350 C (to accuracy of +/- / square) plots for 500 C (to accuracy of +/- / square) lines of best fit (sensible smooth curves) (ignore below 50 atm.) (must not join the dots and each curve must be a single line) for mark each 4 Page 7 of 3

18 read accurately from their graph (must be 350 C and pressure read to +/ half square from their graph) for one mark (iii) smooth curve drawn between 350 o C and 500 C - must be of similar shape to the other curves - a dashed line would be accepted here but would not be accepted for part (i) for one mark (i) reversible reaction (owtte) / equilibrium / equilibria / reaction goes in both directions etc. for one mark maximum of marks from each section up to a maximum total of 5 effect of temperature (max. marks) best yield at low temperature / poor yield at high temperature reaction too slow at low temperature / fast at high temperature effect of pressure (max. marks) high yield at high pressure (owtte) / low yield at low pressure ideas to do with cost / safety factor of using higher pressures evaluation (max. marks) formation of ammonia favoured at low temperature because reaction is exothermic formation of ammonia favoured at high pressure because more reactant molecules than product molecules actual temperature and / or pressure used are a compromise between good yield and reasonable rate ammonia removed / unreacted nitrogen and hydrogen recycled so rate more important than yield catalyst used (not a wrongly named catalyst) for mark each (c) (i) NH 4 NO 3 = 4 + (4 ) (3 6) = 80 (ignore units) for one mark 5 ecf (error carried forward from part (i)) look for (8/80) for first mark gains mark but 35% (% sign not needed) special case of (4/80 00 = 7.5%) gains one mark gains marks [5] Page 8 of 3

19 M6. (a) (i) yield increases two marks are linked because more (gaseous) reactant molecules / particles than (gaseous) product molecules / particles accept 7 4 moles or volumes ignore more reactants accept fewer particles on the right increased (rate) / faster / speeds up etc two marks are linked more collisions or increased concentration or particles closer together greater chance of more successful collisions heat / high temperatures do not accept burn it ignore cracking / catalyst [5] M7. (a) fewer product molecules than reactant molecules (owtte) or accept forward reaction produces fewer molecules accept left hand side for reactants and right hand side for products 3 reactant molecules and product or 3 volumes of gas becomes volume of gas accept high pressure favours the side with fewer molecules ignore references to reaction rate Page 9 of 3

20 any three from: low temperature gives best yield accept add heat as increased temperature or less as poor yield or high temperature gives poor yield because the reaction is exothermic accept reverse argument if clearly expressed reaction too slow at low temperature or reaction faster at high temperature accept add heat and reaction goes faster temperature used gives a reasonable yield at a fast rate / compromise explained allow get less product but it takes less time for marks 3 [4] M8. (a) (i) (gas X) nitrogen/n (gas Y) hydrogen/h cooled any two from: save materials/resources save energy/fuels reduce costs reduce waste (c) (i) low high 40(%) Page 0 of 3

21 (iii) any two from: using these conditions the yield is still high higher pressures would increase yield but energy costs would be higher or higher pressures would increase yield but would make the plant expensive to build the temperature of 450 C would not need a lot of energy or at 450 C the reaction would be faster than at lower temperatures [0] M9. (a) catalyst accept speeds up reaction or lowers activation energy (i) an equilibrium is achieved when rate of the forward reaction is exactly the same as the rate of the backward reaction in this equilibrium the forward reaction to form ammonia is exothermic therefore if the temperature is low the yield from the exothermic reaction increases (iii) in this gaseous equilibrium if the pressure is high this will favour the reaction that produces the least number of molecules, that is, the forward reaction to form ammonia [5] M30. (a) catalyst accept speeds up reaction or lowers activation energy (i) an equilibrium is achieved when rate of the forward reaction is exactly the same as the rate of the backward reaction Page of 3

22 in this equilibrium the forward reaction to form ammonia is exothermic therefore if the temperature is low the yield from the exothermic reaction increases (iii) in this gaseous equilibrium if the pressure is high this will favour the reaction that produces the least number of molecules, that is, the forward reaction to form ammonia [5] Page of 3

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