Pearson Edexcel International GCSE in Chemistry (4CH1) Paper 2CR Mark Scheme January 2020 PDF

PMT Mark Scheme (Results) January 2020 Pearson Edexcel International GCSE in Chemistry (4CH1) Paper 2CR  PMT Edexcel and BTEC Qualifications Edexcel and BTEC qualifications are awarded by Pearson, the UK’s larges...

PMT Mark Scheme (Results) January 2020 Pearson Edexcel International GCSE in Chemistry (4CH1) Paper 2CR  PMT Edexcel and BTEC Qualifications Edexcel and BTEC qualifications are awarded by Pearson, the UK’s largest awarding body. We provide a wide range of qualifications including academic, vocational, occupational and specific programmes for employers. For further information visit our qualifications websites at www.edexcel.com or www.btec.co.uk. Alternatively, you can get in touch with us using the details on our contact us page at www.edexcel.com/contactus. Pearson: helping people progress, everywhere Pearson aspires to be the world’s leading learning company. Our aim is to help everyone progress in their lives through education. We believe in every kind of learning, for all kinds of people, wherever they are in the world. We’ve been involved in education for over 150 years, and by working across 70 countries, in 100 languages, we have built an international reputation for our commitment to high standards and raising achievement through innovation in education. Find out more about how we can help you and your students at: www.pearson.com/uk January 2020 Publications Code 4CH1_2CR_msc_20200305 All the material in this publication is copyright © Pearson Education Ltd 2020  PMT General Marking Guidance All candidates must receive the same treatment. Examiners must mark the first candidate in exactly the same way as they mark the last. Mark schemes should be applied positively. Candidates must be rewarded for what they have shown they can do rather than penalised for omissions. Examiners should mark according to the mark scheme not according to their perception of where the grade boundaries may lie. There is no ceiling on achievement. All marks on the mark scheme should be used appropriately. All the marks on the mark scheme are designed to be awarded. Examiners should always award full marks if deserved, i.e. if the answer matches the mark scheme. Examiners should also be prepared to award zero marks if the candidate’s response is not worthy of credit according to the mark scheme. Where some judgement is required, mark schemes will provide the principles by which marks will be awarded and exemplification may be limited. When examiners are in doubt regarding the application of the mark scheme to a candidate’s response, the team leader must be consulted. Crossed out work should be marked UNLESS the candidate has replaced it with an alternative response.  PMT Question Answer Notes Marks number 1 (a) (i) B box 2 1 The only correct answer is B because box 2 contains two different particles in the same space that are not chemically joined A is not correct because box A shows an element C is not correct because box C shows an element D is not correct because box 4 shows a compound (ii) C Boxes 1 and 3 1 The only correct answer is C because boxes 1 and 2 contain one type of atom only. A is not correct because box 2 shows a mixture B is not correct because box 2 shows a mixture D is not correct because box 4 shows a compound (iii) M1 (box 5 shows) two (different) elements ALLOW two (different) 2 types of atoms REJECT mixture for M1 M2 (chemically) bonded (together) ALLOW (chemically) combined/joined (together) M2 DEP on mention of elements/atoms in M1 (b) (i) C number of protons 1 The only correct answer is B because the elements in the periodic table are arranged in order of proton number A is not correct because elements are not arranged in order of mass number B is not correct because elements are not arranged in order of the number of neutrons D is not correct because elements are not arranged in order of reactivity (ii) A electrons in the outer shell 1 The only correct answer is A because elements in the same group of the periodic table have the same number of electrons in the outer shell. B Is not the correct answer because elements in the same period have the same number of shells C elements in the same group do not have the same number of neutrons D is not the correct answer because elements in the same group do not have the same number of protons  PMT Question Answer Notes Marks number 2 (a) M1 level of the water must be below the dyes/start ACCEPT dyes/start line 2 line should be above water level M2 the start line must be drawn in pencil 2 (b) (i) 2 marks for any two conclusions from 3 (the green food colouring) M1 contains (dye) B and (dye) D M2 contains an unknown dye M3 does not contain A or C M4 contains three dyes ALLOW is not pure and 1 mark for a correct explanation of given conclusion for the green food colouring eg (explanation for M1) because has spots at same level (as B and D) eg (explanation for M2) because has a spot at different level (from A B C D) eg (explanation for M3) because has no spots at same level (as A and C) eg (explanation for M4) because has three spots (ii) M1 (distance moved by solvent correctly measured) ALLOW a tolerance of 3 = 9.5 (cm) ±2mm M2 use of Rf = distance moved by the dye C eg 6.2 distance moved by the solvent 9.5 ALLOW ECF from M1 M3 evaluation of Rf eg (6.2) = 0.65(3) (9.5) ALLOW 1-4 sig fig ALLOW ECF from M2 (iii) (dye A) is not soluble in water ALLOW solvent for 1 water  PMT Question Answer Notes Marks number 3 (a) B Precipitation 1 The only correct answer is B the reaction of two solutions to produce an insoluble solid is precipitation. A is not correct because this reaction is not neutralisation C is not correct because this reaction is not a redox reaction D is not correct because this reaction is not thermal decomposition 3 (b) M1 wash the solid with (deionised) water 2 M2 suitable method of drying solid eg dry between ALLOW leave to dry filter papers/on paper towel/in (warm) oven/in a ALLOW leave in a warm desiccator place ALLOW leave for the water to evaporate IGNORE dry it alone REJECT hot oven or any method of direct heating eg Bunsen burner REJECT references (direct or inferred) to silver chloride solution or crystallisation for M1 and M2 No M2 if solid washed after drying 3 (c) Any one from: 1 M1 (hydrochloric acid/it) contains chloride ions ALLOW contains Cl- M2 (hydrochloric acid/it) produces a (white) precipitate with silver nitrate M3 (hydrochloric acid/it) reacts with silver nitrate 3 (d) M1 n(AgNO3 or AgCl) = 0.0025 2 M2 (mass AgCl) = 0.0025 x 143.5 = 0.35(9)g ALLOW ECF from M1 ALLOW one or more sig fig Correct answer without working scores 2 marks.  PMT Question Answer Notes Marks number 4 (a) M1 layers of atoms/positive ions IGNORE layers 2 unqualified REJECT layers of molecules M2 can slide over one another M2 DEP on mention of layers/atoms/ions in M1 4 (b) (i) ions cannot move ALLOW ions are in fixed 1 positions/in a lattice IGNORE no free ions REJECT any reference to electrons (ii) 2Br- → Br2 + 2e- 1 (iii) M1 lead ions (are positive and) are attracted to the ALLOW cathode for 2 negative electrode / Pb2+ (ions) are attracted to the negative electrode negative electrode M2 lead ions gain electrons / Pb2+ (ions) gain ALLOW a correct half electrons (to form lead) equation for M2 IGNORE references to redox ALLOW lead ions get discharged (to form lead) (iv) metal or lead connects the electrodes or completes ALLOW metal or lead 1 the circuit OWTTE conducts electricity ALLOW metal or lead allows electrons to flow  PMT Question Answer Notes Marks number 5 (a) (i) Any two from: 2 M1 (lithium) moves (on the surface) ALLOW floats M2 (lithium) gets smaller/disappears ALLOW dissolves M3 colourless solution forms IGNORE white trail forms REJECT melts / turns into a ball ALLOW temperature increases/heat given off (ii) (when mixed with air) must refer to test and 1 lit spill/splint or flame gives (squeaky) pop result IGNORE squeaky pop test alone ALLOW burns with (squeaky) pop REJECT glowing spill/splint and pop 5 (b) (i) Any one from: 1 M1 more rapid bubbles/fizzing/effervescence M2 turns into a ball ALLOW potassium melts M3 moves more quickly ALLOW gets smaller/disappears more quickly M4 catches alight / burns / produces a flame IGNORE flame colour (ii) M1 potassium has more shells than lithium ALLOW potassium atom 3 is bigger than lithium ALLOW outer shell/electron is further from nucleus M2 (therefore) there is less attraction between the ALLOW more repulsion outer shell/electron and the nucleus (from inner shells) or more shielding (from the nuclear attraction) ALLOW nuclear pull for the outer shell/electron is weaker M3 so the electron in the outer shell is more easily ACCEPT answers in lost terms of lithium for M1, M2 and M3  PMT Question Answer Notes Marks number 5 (c) (i) M1 n(Li) = 0.500 OR 0.0714 3 7 M2 n(H2) = 0.0714 OR 0.0357 ALLOW ECF from M1 2 M3 volume of H2 (= 0.0357 x 24000) = 857 (cm3) ALLOW ECF M2 x 24 000 M3 must be to 3 sig fig Correct answer to 3 sig fig without working scores 3 marks. (ii) M1 n(H2SO4)= 0.02485 x 0.1 OR 0.002485 3 M2 n(LiOH) = 2 x 0.002485 OR 0.00497 ALLOW ECF from M1 M3 concentration of LiOH = 0.0331 (mol/dm3) ALLOW ECF from M2 (M2 ÷ 0.150) ALLOW any number of sig fig except one for M1 M2 and M3 Correct answer without working scores 3 marks.  PMT Question Answer Notes Marks number 6 (a) A description including the following points: 4 M1 (use) fractional distillation / fractionating column / fractionating tower M2 (crude oil) heated / vaporised ALLOW boiled M3 column is cooler at top / hotter at the bottom / idea of temperature gradient M4 fractions condense/collected at different heights ALLOW fractions with OWTTE high(er) boiling OR fractions have different boiling point (ranges) points/large(r) molecules condense/collected near bottom ORA 6 (b) (i) M1 particles/molecules are closer together ALLOW more 2 particles/molecules per unit volume M2 therefore more (successful) collisions per unit time ALLOW more frequent (successful) collisions If reference to particles have more energy/move faster, then 0/2 (ii) M1 (a catalyst provides) an alternative pathway ALLOW a catalyst 2 provides a surface for the reaction to take place on M2 of lower activation energy ALLOW so more collisions/particles have energy greater than the activation energy. 1 (iii) increase the temperature ALLOW heat it up IGNORE references to concentration REJECT increase the surface area  PMT 6 (b) (iv) 3 M1 C2H6 on horizontal line below the reactants M2 activation energy correctly shown and labelled ACCEPT arrow pointing upwards or double headed arrow M3 ΔH correctly shown and labelled ACCEPT arrow pointing from reactants level to product level or double headed arrow ALLOW max 2 for a correctly labelled endothermic reaction (c) find energy needed to break bonds 3 find energy released when bonds form correct evaluation of ΔH Example calculation M1 (4 x 412) + 612 + 436 OR 2696 IGNORE sign ALLOW 1048 M2 (6 x 412) + 348 OR 2820 IGNORE sign ALLOW 1172 M3 -124 if M1 M2 correct -124 without working scores 3 (+)124 scores 2 ALLOW M3 ECF M1 M2  PMT Question Answer Notes Marks number 7 (a) (i) CO2 1 (ii) (otherwise) ethanoic acid will form ALLOW (otherwise) ethanol will be 1 oxidised or react with oxygen ALLOW fermentation/reaction/respiration needs to be anaerobic ALLOW (otherwise) ethanol would not be formed /CO2 and H2O would be formed (iii) M1(reaction is catalysed by) enzymes (in yeast) IGNORE yeast unqualified 2 M2 which will denature (above 40°C) ALLOW enzymes do not work above 40°C 2 (iv) M1 maximum mass of ethanol = 8 x 46 = 368 (g) M2 55.2 x 100 (=15%) 368 Alternative method: M1 actual yield of ethanol in mol = 55.2 = 1.2 46 M2 1.2 x 100 (=15%) 8 (b) (i) M1 rate of the forwards reaction = the rate of IGNORE it is reversible reaction 2 the backwards reaction M2 the concentrations of reactants and REJECT concentrations of products remain constant reactants and products are equal or are the same (b) (ii) M1 an increase in temperature shifts the IGNORE references to Le 2 (position of) equilibrium in the endothermic Chatelier’s Principle direction (so backwards reaction is ALLOW heating for increase in endothermic) temperature M2 so forward reaction is exothermic M2 DEP M1 or near miss  PMT 7 (c) (i) M1 (displayed formula of A - propanoic acid) ALLOW 1 mark if both OH but 2 otherwise correct M2 (displayed formula of B - butan-1-ol) (c) (ii) M1 add a named carbonate or ALLOW correct formula 2 hydrogencarbonate M2 effervescence/bubbles/fizzing M2 DEP M1 or near miss ALLOW carbon dioxide/CO2 produced REJECT incorrect gas OR M1 add a suitable named metal e.g. ALLOW correct symbol magnesium, aluminium, zinc, iron REJECT a metal that is too reactive e.g. potassium or too unreactive e.g. copper M2 effervescence/bubbles/fizzing M2 DEP M1 or near miss ALLOW hydrogen/H2 produced REJECT incorrect gas OR M1 add a named alcohol (and some ALLOW correct formula concentrated sulfuric acid and warm) M2 sweet smell (of an ester) M2 DEP M1 or near miss  PMT Pearson Education Limited. 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