Science: Chemistry Unit C2 Higher Tier THURSDAY 20 JUNE, AFTERNOON

Transcription

1 Separate Chemistry. Unit pages in total here. General Certificate of Secondary Education 2013 Science: Chemistry Unit C2 Higher Tier [GCH22] THURSDAY 20 JUNE, AFTERNOON *GCH22* *GCH22* TIME 1 hour 45 minutes. INSTRUCTIONS TO CANDIDATES Write your Centre Number and Candidate Number in the spaces provided at the top of this page. You must answer the questions in the spaces provided. Do not write outside the box, around each page or on blank pages. Complete in blue or black ink only. Do not write with a gel pen. Answer all questions. INFORMATION FOR CANDIDATES The total mark for this paper is 115. Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question. Quality of written communication will be assessed in question 5(a). A Data Leaflet, which includes a Periodic Table of the Elements, is included in this question paper. *24GCH2201* *24GCH2201*

2 1 Fireworks contain the three ingredients shown in the box below. Examiner Only Marks Remark colouring agent fuel oxidiser (a) Magnesium is often used in fireworks as the colouring agent. (i) What is the colour of the flame observed when magnesium burns? (ii) Write a balanced symbol equation for magnesium burning in air. [3] (b) Carbon in the form of charcoal is often used as the fuel in fireworks. (i) What is observed when a sample of carbon burns? [2] (ii) Name the product formed when carbon burns in a limited supply of oxygen *24GCH2202* *24GCH2202*

3 (c) Oxidisers provide the oxygen needed to allow the firework to burn effectively. A common oxidiser is potassium nitrate, which thermally decomposes to produce potassium oxide, nitrogen and oxygen. Examiner Only Marks Remark Write a balanced symbol equation for this reaction. [3] (d) Sparklers are hand held fireworks which contain a fuel, an oxidiser and iron powder. Often the iron powder is mixed with linseed oil to prevent it rusting. (i) What conditions are required for iron to rust? [2] (ii) What is the chemical name for rust? [2] 7952 [Turn over *24GCH2203* *24GCH2203*

4 (e) In industry, iron is manufactured in the Blast Furnace. A redox reaction which occurs in the Blast Furnace is given below: Examiner Only Marks Remark Fe 2 O 3 3CO 2Fe 3CO 2 Explain fully, in terms of change in oxygen content, why this reaction is described as a redox reaction. [5] Total Question *24GCH2204* *24GCH2204*

5 2 (a) The rate of decomposition of a solution of hydrogen peroxide using manganese(iv) oxide (manganese dioxide) can be measured using the apparatus shown below. The manganese(iv) oxide is a catalyst for the reaction. Examiner Only Marks Remark CCEA (i) Name the piece of apparatus labelled A. (ii) What is meant by the term catalyst? [3] (iii) Write a balanced symbol equation for the decomposition of hydrogen peroxide. [3] 7952 [Turn over *24GCH2205* *24GCH2205*

6 (b) The graph below shows data obtained at 25 C using 25.0 cm 3 of 0.16 mol/dm 3 hydrogen peroxide solution with 1.0 g of solid powdered manganese(iv) oxide Gas volume/cm Time/s (i) Apart from the apparatus shown in the diagram in part (a), name one other piece of equipment which would be required to collect the results used to draw the graph. Examiner Only Marks Remark (ii) What was the total volume of gas collected? (iii) The reaction was repeated at 40 C with all other factors being kept the same. Sketch the graph you would expect to obtain on the axes above. [3] 7952 *24GCH2206* *24GCH2206*

7 (c) The table below shows the time taken for the decomposition of hydrogen peroxide solution to be completed cm 3 of 0.16 mol/dm 3 hydrogen peroxide solution was used with 1.0 g of different powdered metal oxides as catalysts. Examiner Only Marks Remark Metal oxide Time for decomposition to be completed/s Rate of decomposition/s 1 1 rate time Manganese(IV) oxide Copper(II) oxide Zinc oxide (i) Using the graph at 25 C in part (b), complete the table above. [2] (ii) State which of the metal oxides in the table is the least effective catalyst and explain your answer. [2] Total Question [Turn over *24GCH2207* *24GCH2207*

8 3 Perfume is a mixture of essential oils dissolved in a solvent. One of the essential oils used in making perfume is called myrcene. Examiner Only Marks Remark istockphoto / Thinkstock (a) The structural formula of a molecule of myrcene is shown below. H H H H H C H H H C H H C C C C C C C C H H H H H H (i) Explain why a molecule of myrcene can be classified as a hydrocarbon. (ii) Identify the functional group present in myrcene *24GCH2208* *24GCH2208*

9 (b) Linalool is another essential oil used in perfume making. It gives a sweet, lavender-like smell. The structural formula of linalool is shown below. Examiner Only Marks Remark H H H OH H H H H C H H C C C C C C C C H H H C H H H H H (i) On the structure of linalool shown above, draw a circle around the alcohol functional group. (ii) Like all alcohols, linalool (C 10 H 17 OH) undergoes complete combustion in excess air. Complete and balance the symbol equation below for this reaction. C 10 H 17 OH O 2 [2] (iii) When linalool is warmed with acidified potassium dichromate solution it is oxidised in the same way as ethanol. State the colour change which is observed in this reaction. from to [2] 7952 [Turn over *24GCH2209* *24GCH2209*

10 (c) Ethanol is an alcohol which is often used as a solvent in perfumes. (i) Write the general formula for alcohols. Examiner Only Marks Remark (ii) Draw the structural formula of ethanol. (iii) Ethene can be used to manufacture the ethanol used in perfumes. Complete the table below to give information about ethene. Name Molecular formula Structural formula State at room temperature and pressure Ethene [3] 7952 *24GCH2210* *24GCH2210*

11 (d) Ethanoic acid is a carboxylic acid which can be used to make other solvents. These solvents are also used in perfumes. Examiner Only Marks Remark (i) Draw the structural formula of ethanoic acid. (ii) State two observations you would make when magnesium reacts with ethanoic acid. [2] (iii) Write a balanced symbol equation for the reaction of magnesium with ethanoic acid. [3] Total Question [Turn over *24GCH2211* *24GCH2211*

12 4 Metals may be placed in a reactivity series by observing their reactions with air, water, steam and dilute acid. Examiner Only Marks Remark (a) The apparatus below may be used to react zinc metal with steam. damp mineral wool zinc gas produced A B HEAT HEAT trough water beehive shelf Barking Dog Art (i) What labels should be placed at A and B on the diagram? A B [2] (ii) Explain why the damp mineral wool is heated. (iii) Name the gas produced in this experiment. (iv) Name a metal which does not react when heated with steam *24GCH2212* *24GCH2212*

13 (b) X is an unknown metal. The table below gives details of some reactions of the three metals X, sodium and zinc. Examiner Only Marks Remark Metal Reaction when heated in oxygen Reaction with cold water Reaction with dilute hydrochloric acid X Black coating forms on metal without burning No reaction No reaction Sodium Burns very vigorously with a yellow flame Dangerous reaction not carried out in school laboratory Zinc Burns forming a yellow solid which changes to white on cooling No reaction Reacts steadily (i) Suggest the name of metal X. (ii) Describe what you would observe when sodium reacts with cold water. [3] (iii) Write a balanced symbol equation for the reaction of sodium with water. [3] 7952 [Turn over *24GCH2213* *24GCH2213*

14 (c) Aluminium is a metal which is extracted from its ore (bauxite) by electrolysis. Examiner Only Marks Remark (i) What is meant by the term electrolysis? [2] (ii) What is the name of the purified bauxite which is used in the production of aluminium by electrolysis? (iii) Write a half equation to represent the production of aluminium during this electrolysis process. [3] (iv) At what temperature is this electrolysis carried out? (v) Explain why the carbon anodes need to be replaced periodically during this electrolysis. [3] Total Question *24GCH2214* *24GCH2214*

15 5 Alkaline batteries contain one particular metal hydroxide. The metal hydroxide can be represented as MOH. Examiner Only Marks Remark istockphoto / Thinkstock 3.92 g of this solid metal hydroxide were dissolved in 1000 cm 3 of deionised water in a volumetric flask cm 3 of this solution were placed in a conical flask using a pipette. (a) Describe in detail how you would prepare and use a pipette to transfer 25.0 cm 3 of the MOH solution into a conical flask, ensuring accuracy and safety. In this question you will be assessed on using your written communication skills including the use of specialist scientific terms. [6] 7952 [Turn over *24GCH2215* *24GCH2215*

16 (b) 25.0 cm 3 of the MOH solution were titrated with hydrochloric acid of concentration mol/dm 3 using phenolphthalein indicator. The results are shown in the table below. Examiner Only Marks Remark Initial burette volume/cm 3 Final burette volume/cm 3 Titre/cm 3 Rough titration First accurate titration Second accurate titration (i) Calculate the average titre. cm 3 [2] (ii) State the colour change at the end-point. From to [2] (iii) Calculate the number of moles of hydrochloric acid used in the titration. The balanced symbol equation for the reaction is: [2] MOH HCl MCl H 2 O 7952 *24GCH2216* *24GCH2216*

17 (iv) Calculate the number of moles of MOH present in 25.0 cm 3 of the solution in the conical flask. Examiner Only Marks Remark (v) Calculate the number of moles of MOH present in 1000 cm 3 of the solution. [2] (vi) Using the fact that 3.92 g of MOH were dissolved in 1000 cm 3 and the answer to question (b)(v) above, determine the relative formula mass of MOH. [2] 7952 [Turn over *24GCH2217* *24GCH2217*

18 (vii) Determine the relative atomic mass of M using your answer to question (b)(vi). (Relative atomic masses: H 1; O 16) Examiner Only Marks Remark [2] (viii) Identify the metal, M. Total Question *24GCH2218* *24GCH2218*

19 6 (a) An investigation was carried out to compare the hardness of water samples from three towns A, B and C. Examiner Only Marks Remark 25 cm 3 of each water sample were placed into three separate conical flasks and labelled A, B and C. A sample of deionised water was also tested. Soap solution was added, 1 cm 3 at a time, to each conical flask with shaking until a lasting lather formed. The total volume of soap solution added to each flask was recorded. The experiment was repeated with fresh samples of A, B and C which had been boiled and allowed to cool, before adding the soap solution. The results are shown in the table below. Water sample Volume of soap solution required to form a lather before boiling (cm 3 ) after boiling (cm 3 ) Deionised water 2 2 A 6 6 B 8 2 C 11 7 (i) Which of the three water samples (A, B or C) is the hardest water? (ii) Which of the three water samples (A, B or C) contains only temporary hardness? (iii) Which of the three water samples (A, B or C) contains both temporary and permanent hardness? 7952 [Turn over *24GCH2219* *24GCH2219*

20 (b) Permanent hardness may be removed from water by the addition of washing soda. Explain, in terms of ions, how washing soda can soften hard water. Examiner Only Marks Remark [3] (c) State two disadvantages of hard water [2] Total Question *24GCH2220* *24GCH2220*

21 7 Nitrogenous fertilisers contain ammonium compounds such as ammonium nitrate which is produced when ammonia reacts with nitric acid. Examiner Only Marks Remark (a) (i) Write a balanced symbol equation for the reaction of ammonia with nitric acid. [2] (ii) Describe how you would carry out a chemical test for the presence of ammonia gas, stating the observations you would make for a positive test. [4] (iii) State one disadvantage of using nitrogenous fertilisers. (b) In industry ammonia gas is produced by the Haber process which involves a reversible reaction between the gases nitrogen and hydrogen. N 2 3H 2 2NH 3 (i) Explain what you understand by the term reversible reaction. (ii) Name the catalyst used in the Haber process [Turn over *24GCH2221* *24GCH2221*

22 (c) The percentage yield of ammonia produced in the Haber Process is affected by both the temperature and the pressure. The graph below shows how the percentage yield of ammonia changes with temperature and pressure. Examiner Only Marks Remark C 50 % Yield of ammonia C 550 C Pressure/atm Use the graph to answer the following questions. (i) State the effect of increasing temperature on the yield of ammonia at constant pressure. (ii) 450 C and 250 atm are commonly used conditions for the Haber Process. What is the percentage yield of ammonia using these conditions? 7952 *24GCH22B* *24GCH2222*

23 (iii) Suggest why industry uses 450 C and 250 atm when it is possible to obtain a higher yield of ammonia using a lower temperature and a higher pressure. Examiner Only Marks Remark THIS IS THE END OF THE QUESTION PAPER Total Question *24GCH2223* *24GCH2223*

24 General Certificate of Secondary Education 2013 Science: Chemistry Unit C2 Higher Tier [GCH22] THURSDAY 20 JUNE, AFTERNOON MARK SCHEME F

25 1 (a) (i) white (ii) 2Mg + O 2 2MgO for correct formulae of reactants for correct formula of product for correct balancing [3] AVAILABLE MARKS (b) (i) black solid (at beginning) flame/glows/sparks appropriate colour sooty/smoky (white/grey) ash formed/no solid remaining heat released max [2] (ii) carbon monoxide (c) 4KNO 3 2K 2 O + 5O 2 + 2N 2 for correct formula of reactant for correct formulae of products for correct balancing [3] (d) (i) water/moisture air/oxygen [2] (ii) hydrated iron(iii) oxide [2] (e) iron oxide loses oxygen reduction is loss of oxygen carbon monoxide gains oxygen oxidation is the gain of oxygen redox is oxidation and reduction occurring simultaneously [5] F 3

26 2 (a) (i) gas syringe (ii) substance which increases the rate of a (chemical) reaction without being used up/without being chemically changed at the end [3] AVAILABLE MARKS (iii) 2H 2 O 2 2H 2 O + O 2 for correct formula of reactant for correct formulae of products for correct balancing [3] (b) (i) any second accurate timing device, e.g. (stop)clock/(stop)watch (ii) 48 (cm 3 ) (iii) starts at (0,0) and remains higher throughout/steeper gradient finishes at same gas volume/48 cm 3 finishes in less time/earlier [3] (c) (i) time is rate is to [2] (ii) zinc oxide largest time/smallest or lowest rate [2] 16 second mark dependent on first mark F 4

27 3 (a) (i) (the molecule of myrcene) contains only carbon and hydrogen (ii) C C AVAILABLE MARKS (b) (i) OH group identified (ii) C 10 H 17 OH + 14 O 2 10 CO H 2 O for correct formulae of products for balancing [2] (iii) orange to green [2] (c) (i) C n H 2n+1 OH (ii) H H H C C OH H H (iii) Name Molecular formula Structural formula State at room temperature and pressure H H Ethene C 2 H 4 C C gas H H [3] (d) (i) H H C C H O O H (ii) bubbles/effervescence magnesium disappears heat released colourless solution remains max [2] (iii) Mg + 2CH 3 COOH (CH 3 COO) 2 Mg + H 2 [3] F 5

28 4 (a) (i) A delivery tube B gas jar [2] AVAILABLE MARKS (ii) generate steam (iii) hydrogen (iv) copper/silver/gold/platinum/palladium (b) (i) copper (ii) any three from: floats/on surface moves about melts to form a silvery ball fizzing/gas produced colourless solution formed metal disappears heat released [3] (iii) 2Na + 2H 2 O 2NaOH + H 2 for correct formulae of reactants for correct formulae of products for correct balancing [3] (c) (i) decomposition using (a direct current of) electricity [2] (ii) alumina (iii) Al e Al for Al 3+ and e on left hand side for Al on right hand side for correct balancing of electrons [3] (iv) C (v) anode/carbon reacts with oxygen forming carbon dioxide carbon anodes are worn away [3] F 6

29 5 (a) Indicative content safety pipette filler used rinse pipette rinsed with (deionised) water pipette rinsed with MOH solution fill with MOH solution filling until bottom of meniscus on the line release into conical flask transfer touch tip of pipette onto surface of liquid AVAILABLE MARKS Accept alternative appropriate responses Response Candidates must use appropriate specialist terms throughout to discuss fully the preparation and use of a pipette with regard to safety and accuracy in a logical sequence (6 7 points). They use good spelling, punctuation and grammar and the form and style are of a high standard. Candidates use some appropriate specialist terms to discuss the preparation and use of a pipette with regard to safety and accuracy (3 5 points). They use satisfactory spelling, punctuation and grammar and the form and style are of a satisfactory standard. Candidates describe the preparation and use of a pipette with regard to safety and accuracy which may not be in a logical sequence (using a minimum of 2 points). They use limited spelling, punctuation and grammar and form and style are of a limited standard. Mark [5] [6] [3] [4] [2] Response not worthy of credit [0] [6] (b) (i) 14.0 [2] [2] award for 14.3 which includes use of rough titration value (ii) pink to colourless [2] (wrong way round ) (iii) = [2] (iv) (v) = 0.07 [2] (vi) 3.92 = 56 [2] 0.07 (vii)oh = 17 M = = 39 [2] (viii) potassium/k F 7

30 6 (a) (i) C (ii) B AVAILABLE MARKS (iii) C (b) Ca 2+ /calcium ions/mg 2+ /magnesium ions react reaction with CO 3 2 /carbonate ions forming insoluble/solid CaCO 3 /magnesium carbonate [3] (c) wastes soap produces limescale in kettles/hot water pipes/irons etc. qualified cost (more electricity used, purchase of ion exchanger/ dishwasher salt) forms scum with soap max [2] 8 7 (a) (i) NH 3 + HNO 3 NH 4 NO 3 [2] (ii) dip glass rod into concentrated hydrochloric acid apply to gas white smoke/solid [4] (iii) blue baby syndrome/stomach cancer/eutrophication (b) (i) idea that reaction can move from right to left as well as from left to right (ii) iron (c) (i) decreases (ii) 30% (iii) compromise between temperature and pressure/rate and yield/ catalyst does not work at low temperatures/pressure expensive to apply 12 Total F 8

31 Centre Number Candidate Number General Certificate of Secondary Education 2014 GCSE Chemistry Unit 2 Higher Tier *GCH22* [GCH22] THURSDAY 19 JUNE, AFTERNOON *GCH22* TIME 1 hour 45 minutes. INSTRUCTIONS TO CANDIDATES Write your Centre Number and Candidate Number in the spaces provided at the top of this page. You must answer the questions in the spaces provided. Do not write outside the box, around each page or on blank pages. Complete in blue or black ink only. Do not write with a gel pen. Answer all seven questions. INFORMATION FOR CANDIDATES The total mark for this paper is 115. Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question. Quality of written communication will be assessed in Questions 2 and 4(a). A Data Leaflet, which includes a Periodic Table of the Elements, is included in this question paper R *24GCH2201* *24GCH2201*

32 DO NOT WRITE ON THIS PAGE *24GCH2202* *24GCH2202*

33 1 Many multivitamin supplements are produced as tablets which effervesce when added to water. The label of a multivitamin supplement is shown below. Examiner Only Marks Multivitamin Supplement Niacin Calcium carbonate Vitamin B12 Sweeteners Salt Orange flavouring Citric acid In an experiment one multivitamin tablet was added to 50 cm 3 of water in a conical flask at a temperature of 20 C. The flask was loosely stoppered with a cotton wool plug and placed on an electronic balance. A stopclock was started as soon as the tablet made contact with the water. The mass was recorded every 20 seconds. (a) Draw a labelled diagram of the assembled apparatus used to carry out this experiment. Include all apparatus. [4] R [Turn over *24GCH2203* *24GCH2203*

34 (b) The results obtained from the experiment are shown below. Examiner Only Marks Remark Time/s Mass/g (i) Plot these results on the graph below. [4] Mass/g Time/s R *24GCH2204* *24GCH2204*

35 Using the graph answer the following questions. Examiner Only Marks Remark (ii) At what time does the reaction stop? (iii) Calculate the total loss in mass. (iv) The experiment was repeated using one tablet and 50 cm 3 of water at 40 C. On the same axes, sketch the graph for this experiment and label it B. [3] (v) State and explain, in terms of particles, the effect of increasing temperature on the rate of a chemical reaction. [3] (c) Explain what you understand by the term activation energy. [2] Total Question R [Turn over *24GCH2205* *24GCH2205*

36 2 Concentrated sulfuric acid is manufactured industrially by the Contact Process. This process occurs in four stages, one of which requires three specific conditions. Examiner Only Marks Remark Describe the chemistry of the Contact Process. Your answer should include the following: balanced symbol equations for each of the four stages names of all reactants and products in each reaction identification of the stage which requires specific conditions details of these conditions In this question you will be assessed on your written communication skills including the use of specialist scientific terms R *24GCH2206* *24GCH2206*

37 Examiner Only Marks Remark [12] Total Question R [Turn over *24GCH2207* *24GCH2207*

38 3 The diagram below shows the Earth s solar system. Examiner Only Marks istock / Thinkstock (a) Mars is often called the red planet due to the presence of haematite on its surface. A recent study of the Huygens Crater on Mars has also shown the presence of iron(iii) hydroxide and calcium carbonate. (i) Calcium carbonate and iron(iii) hydroxide undergo thermal decomposition. What is meant by the term thermal decomposition? [2] (ii) Write a balanced symbol equation for the thermal decomposition of iron(iii) hydroxide into iron(iii) oxide and water. [3] R [Turn over *24GCH2209* *24GCH2209*

39 (b) Mars does not have tectonic plates but Earth does. What may occur at the boundaries between tectonic plates? Examiner Only Marks Remark [2] (c) Atmosphere is the term used to describe the collection of gases that surround a planet. The composition of the atmosphere of Mars is shown in the table below. Gas Composition Carbon dioxide 95.0% Nitrogen 3.0% Noble gases 1.6% Oxygen Methane trace trace Compare the composition of the Earth s atmosphere today, with that of the planet Mars. [5] R *24GCH2210* *24GCH2210*

40 (d) Changes in the atmosphere of the Earth occurred slowly over millions of years due to photosynthesis and other processes. Examiner Only Marks Remark (i) An unbalanced symbol equation for the production of glucose (C 6 H 12 O 6 ) in photosynthesis is shown below. Balance this equation. CO 2 1 H 2 O C 6 H 12 O 6 1 O 2 (ii) Photosynthesis is an endothermic reaction. In terms of bonds, explain why this reaction is endothermic. [5] Total Question R [Turn over *24GCH2211* *24GCH2211*

41 4 The water supply in some parts of Northern Ireland may be described as being hard water. Examiner Only Marks Remark (a) Describe in detail how a sample of water may be tested for hardness. Your answer should include: how to determine that hardness is present in the water how to determine if the hardness present is temporary or permanent all practical details In this question you will be assessed on your written communication skills including the use of specialist scientific terms. [6] R *24GCH2212* *24GCH2212*

42 (b) Temporary hard water is found in areas where limestone rock is common. Examiner Only Marks Remark (i) Write a balanced symbol equation to show the formation of temporary hard water. [2] (ii) Describe in detail how temporary hardness arises in water. [3] (iii) State two methods which may be used to remove permanent hardness from water [2] Total Question R [Turn over *24GCH2213* *24GCH2213*

43 5 (a) A homologous series is a family of organic compounds that have the same general formula and show a gradation in physical properties. Examiner Only Marks Remark (i) State one other feature of a homologous series. (ii) Alkanes and alkenes are examples of homologous series. Complete the following table. Name of homologous series General formula Molecular formula of compound with three carbon atoms Alkanes C 3 H 8 Alkenes C n H 2n [2] (iii) Name the alkane with the molecular formula C 3 H 8. (b) Alkanes and alkenes undergo combustion reactions. (i) What is meant by the term combustion? [3] (ii) Write a balanced symbol equation for the complete combustion of methane. [3] R *24GCH2214* *24GCH2214*

44 (c) Alkenes contain the C C functional group. (i) What do you understand by the term functional group? Examiner Only Marks Remark (ii) Describe a chemical test which may be used to confirm the presence of the C C in an alkene. State the result you would expect for a positive test. [3] (d) Alkenes undergo addition polymerisation to form polymers such as polythene and PVC (polyvinyl chloride). (i) Write a structural equation to show the formation of PVC. [4] (ii) State one reason why PVC is used to make window frames in preference to wood R [Turn over *24GCH2215* *24GCH2215*

45 (e) The structures of four organic compounds are shown below. Examiner Only Marks Remark H H O H C OH H A H C C H B OH H H H H H H H C C C C H C C H H H H H H C D (i) Name compound A. (ii) What is the functional group in compound B? (iii) Explain why compound C is a hydrocarbon. (iv) Which compound (A, B, C or D) reacts with sodium carbonate? Total Question R *24GCH2216* *24GCH2216*

46 6 A reactivity series of some metals is shown below: Examiner Only Marks Remark potassium sodium calcium magnesium aluminium iron copper reactivity increases (a) Silver metal does not appear on the above reactivity series. Copper metal will react with silver nitrate solution to form silver as shown below. copper wire silver nitrate solution silver forming on the surface of copper wire Peticolas/Megna/Fundemental Photos / Science Photo Library (i) Write a balanced symbol equation for the reaction of copper with silver nitrate forming silver and copper(ii) nitrate. [3] (ii) Indicate the position of silver on the reactivity series shown above R [Turn over *24GCH2217* *24GCH2217*

47 (iii) Silver nitrate solution is colourless. What is the colour of the solution at the end of this reaction? Examiner Only Marks Remark (iv) Explain why copper displaces silver from a solution of silver nitrate. [2] (b) Silver particles of size 1 to 100 nanometres (nm) are used to kill bacteria in wound dressings. (i) Explain what you understand by a nanometre. (ii) Describe one risk which has been associated with the use of silver particles of this size. (c) Aluminium is a very useful metal due to its high electrical conductivity, relatively low density and lack of reactivity. (i) Explain why aluminium shows a lack of reactivity even though the reactivity series would suggest it is a moderately reactive metal. [3] R *24GCH2218* *24GCH2218*

48 (ii) A balanced symbol equation for a reaction of aluminium is shown below: Examiner Only Marks Remark 2Al 1 3CuO Al 2 O 3 1 3Cu Write a word equation for this reaction. [2] Total Question R [Turn over *24GCH2219* *24GCH2219*

49 7 Homemade wines contain acids such as tartaric acid. Examiner Only Marks Remark (a) Tartaric acid has the molecular formula C 4 H 6 O 6. Calculate the percentage of oxygen present in tartaric acid. Percentage of oxygen [3] (b) To find the concentration of acid in their homemade wine, wine makers can use a wine testing kit. The label of a wine testing kit is shown below. WINE TESTING KIT 25 cm 3 syringe 30 cm 3 syringe 0.1 mol/dm 3 sodium hydroxide solution Phenolphthalein indicator Plastic beaker The instructions on the wine testing kit are: Measure out 25 cm 3 of wine into the plastic beaker using the 25 cm 3 syringe. Add 3 drops of phenolphthalein indicator. Slowly add sodium hydroxide from the other syringe until the indicator changes colour. State the colour change observed for the phenolphthalein indicator. From to [2] R *24GCH2220* *24GCH2220*

50 (c) This method can be carried out more accurately in a laboratory using titration apparatus. Examiner Only Marks Remark (i) Name the piece of apparatus used to measure out accurately 25.0 cm 3 of wine. (ii) Name the piece of apparatus used to accurately add the sodium hydroxide solution to the wine in a titration. (iii) This method is suitable for white wine. Suggest why it is not used to find the concentration of acid in red wine. QUESTION 7 CONTINUES OVERLEAF R [Turn over *24GCH2221* *24GCH2221*

51 (d) In a laboratory experiment 25.0 cm 3 of white wine were placed in a conical flask and a few drops of phenolphthalein indicator added. Sodium hydroxide solution of concentration 0.1 mol/dm 3 was then added slowly to the conical flask. The results of the titration are shown in the table below. Examiner Only Marks Remark Initial reading (cm 3 ) Final reading (cm 3 ) Titre (cm 3 ) Titration 1 (rough) Titration Titration (i) Calculate the average titre. Average titre cm 3 [2] (ii) Calculate the number of moles of sodium hydroxide solution used in this titration. Moles of sodium hydroxide [2] R *24GCH2222* *24GCH2222*

52 (iii) The equation for the reaction of the tartaric acid in the white wine with sodium hydroxide is shown below. Use this equation to calculate the number of moles of tartaric acid which reacted with the sodium hydroxide solution. Examiner Only Marks Remark C 4 H 6 O 6 1 2NaOH C 4 H 4 O 6 Na 2 1 2H 2 O Moles of tartaric acid [2] (iv) Calculate the concentration of the tartaric acid in mol/dm 3. Concentration of tartaric acid mol/dm 3 [2] (v) Calculate the concentration of the tartaric acid in g/dm 3. Concentration of tartaric acid g/dm 3 Total Question 7 THIS IS THE END OF THE QUESTION PAPER R *24GCH2223* *24GCH2223*

53 General Certificate of Secondary Education 2014 GCSE Chemistry Unit 2 Higher Tier [GCH22] THURSDAY 19 JUNE, AFTERNOON MARK SCHEME F

54 1 (a) conical fl ask with cotton wool plug placed on electronic balance tablet in contact with water timer/stopclock/stopwatch [4] No labels = [0] AVAILABLE MARKS (b) (i) 5 7 points plotted correctly [3] 2 4 points plotted correctly [2] 1 point plotted correctly smooth curve [4] (ii) seconds units essential (iii) 1.10 g units essential allow 1.1 g (iv) graph starts at (0, 234.1) and remains lower levels off earlier levels off at same mass reading as initial graph [3] (v) particles have more energy/move faster idea of more successful collisions per unit time [3] (c) minimum energy which (reactant) particles need to react [2] 18 (energy which particles need to react ) F 3

55 AVAILABLE MARKS Mass/g Time/s F 4

56 2 Indicative content sulfur burns in (oxygen from) air producing sulfur dioxide S + O 2 SO 2 [2] sulfur dioxide reacts with (more) oxygen (from air) forming sulfur trioxide 2SO 2 + O 2? 2SO 3 [3] in the presence of a vanadium(v) oxide catalyst at 450 C and 2 atm pressure (1 10 accepted) sulfur trioxide reacts with concentrated sulfuric acid to form oleum SO 3 + H 2 SO 4 H 2 S 2 O 7 [2] oleum diluted to form sulfuric acid H 2 S 2 O 7 + H 2 O 2H 2 SO 4 [3] AVAILABLE MARKS Response Mark Candidates must use appropriate specialist terms to explain fully the industrial manufacture of sulfuric acid (using a minimum of 11 points of indicative content) [9] [12] including at least three balanced symbol equations and a logical sequence. They use good spelling, punctuation and grammar and the form and style are of a high standard. Candidates must use appropriate specialist terms to explain fully the industrial manufacture of sulfuric acid (using a minimum of 6 points of indicative content) including at least two balanced symbol equations and [5] [8] a logical sequence. They use satisfactory spelling, punctuation and grammar and the form and style are of a satisfactory standard. Candidates explain briefl y and partially the industrial manufacture of sulfuric acid (using a minimum of 2 points of indicative content) including at least one balanced [4] symbol equation. They use limited spelling, punctuation and grammar and they have made little use of specialist terms. The form and style are of a limited standard. Response not worthy of credit [0] [12] 12 Award indicative content marks for catalyst and conditions only if referring to correct stage F 5

57 3 (a) (i) breaking down (a substance) using heat [2] (ii) 2Fe(OH) 3 Fe 2 O 3 + 3H 2 O for correct formula of reactant for correct formulae of products for correct balancing [3] AVAILABLE MARKS (b) Any two from: volcanoes/earthquakes/mountain formation [2] (c) A comparison of three of the following gases: Nitrogen Oxygen Carbon dioxide Noble gases max [3] Two correct percentages of gases in Earth s atmosphere [2] [5] (d) (i) 6CO 2 + 6H 2 O C 6 H 12 O 6 + 6O 2 for correct balancing (ii) energy taken in to break bonds in carbon dioxide and water is more than energy released when bonds are made in C 6 H 12 O 6 (glucose) and oxygen [5] F 6

58 4 (a) Indicative content Add soap (solution) to sample of water and shake If scum forms/there is no immediate lather, the water is hard Take another sample of the water Boil it Add soap solution and shake If a lather forms temporary hardness If no lather permanent hardness AVAILABLE MARKS Response Mark Candidates must use appropriate specialist terms throughout to describe fully how a sample of water is tested for hardness and how to determine if the hardness is temporary or permanent (6 7 points from the indicative [5] [6] content above) in a logical sequence. They use good spelling, punctuation and grammar and the form and style are of a high standard. Candidates use some appropriate specialist terms to describe how a sample of water is tested for hardness and/or how to determine if the hardness is temporary or permanent (3 5 points from the indicative content above) [3] [4] in a logical sequence. They use satisfactory spelling, punctuation and grammar and the form and style are of a satisfactory standard. Candidates describe how to test a sample of water for hardness and/or how to determine if the hardness is temporary or permanent (1 2 points from the indicative content above) which may not be in a logical sequence. [2] They use limited spelling, punctuation and grammar and they have made little use of specialist terms. The form and style are of a limited standard. Response not worthy of credit [0] [6] (b) (i) CaCO 3 + CO 2 + H 2 O Ca(HCO 3 ) 2 for correct formulae of reactants for correct formula of product [2] (ii) calcium carbonate reacts with (rain)water containing dissolved carbon dioxide forming soluble calcium hydrogen carbonate/forms calcium hydrogen carbonate solution [3] (iii) ion exchange addition of washing soda (allow distillation) [2] F 7

59 5 (a) (i) show similar chemical properties/differ by a CH 2 (unit/group) (ii) Name of homologous series General formula Molecular formula of compound with three carbon atoms AVAILABLE MARKS Alkanes C n H 2n+2 C 3 H 8 Alkenes C n H 2n C 3 H 6 (iii) propane (b) (i) reaction of a fuel reaction with oxygen forming oxides and releasing heat max [3] [3] (ii) CH 4 + 2O 2 CO 2 + 2H 2 O for correct formulae of reactants for correct formulae of products for correct balancing [3] (c) (i) a reactive group in a molecule (d) (i) (ii) bromine water (changes from) red-brown/orange/yellow to colourless [3] [2] for correct structure of the monomer for n before the monomer structure for correct structure of the polymer in [ ] with bonds through the [ ] for repeat indicated in polymer [4] (ii) more durable/does not rot (e) (i) methanol (ii) COOH/carboxyl accept carboxylic acid (iii) only contains carbon and hydrogen (atoms) (iv) B accept CH 3 COOH/ethanoic acid F 8

60 6 (a) (i) 2AgNO 3 + Cu Cu(NO 3 ) 2 + 2Ag for correct formulae of reactants for correct formulae of products for correct balancing [3] AVAILABLE MARKS (ii) silver indicated below copper (iii) blue (iv) copper is more reactive/higher in reactivity series than silver [2] (b) (i) m or other suitable idea of length, e.g mm (ii) unknown effects/absorbed through skin/discolour skin/allergic reaction/damage organs (c) (i) A layer of (aluminium) oxide forms on surface of aluminium which prevents aluminium reacting [3] (ii) aluminium + copper(ii) oxide aluminium oxide + copper for reactants and for products [2] 14 allow copper oxide for copper(ii) oxide 7 (a) = 64 % [3] (b) colourless to pink [2] award for wrong way round (c) (i) pipette (ii) burette (iii) cannot see the colour change of the indicator in red wine (d) (i) 19.0 [2] cm 3 allow 19cm 3 use of rough gives [2] (ii) (iii) (iv) 19 # 0. 1 = [2] = ( ) [2] # 1000 = mol/dm 3 [2] 25 (v) = 5.7 g/dm 3 17 Apply consequential marking throughout (d) Total F 9

61 Centre Number Candidate Number General Certificate of Secondary Education 2015 GCSE Chemistry Unit 2 Higher Tier *GCH22* [GCH22] WEDNESDAY 17 JUNE, MORNING *GCH22* TIME 1 hour 45 minutes. INSTRUCTIONS TO CANDIDATES Write your Centre Number and Candidate Number in the spaces provided at the top of this page. You must answer the questions in the spaces provided. Do not write outside the boxed area on each page or on blank pages. Complete in blue or black ink only. Do not write with a gel pen. Answer all seven questions. INFORMATION FOR CANDIDATES The total mark for this paper is 115. Figures in brackets printed down the right-hand side of pages indicate the marks awarded to each question or part question. Quality of written communication will be assessed in Questions 2(a) and 5(b)(vi). A Data Leaflet, which includes a Periodic Table of the Elements, is included in this question paper *28GCH2201* *28GCH2201*

62 1 (a) Solid calcium chloride absorbs moisture from the air and dissolves in it to form a solution. In solution, calcium chloride causes permanent hardness in water. (i) What is meant by hard water? [2] (ii) What term is used to describe a solid which absorbs moisture from the air and dissolves in it? (iii) Explain the difference between temporary hardness and permanent hardness in water. [2] 9374 [Turn over *28GCH2203* *28GCH2203*

63 (b) Hydrated sodium carbonate can be used to remove permanent hardness from water. (i) What is the common name of hydrated sodium carbonate? (ii) Write an ionic equation to show how hydrated sodium carbonate removes permanent hardness from water. Include state symbols. [3] (iii) State one other method which is used to remove permanent hardness from water. (iv) State one advantage of hardness in a domestic water supply *28GCH2204* *28GCH2204*

64 2 (a) Ethanol can be manufactured by fermentation. Describe the production of ethanol by fermentation. In your answer you should include: the names of the starting materials the conditions required the names of any other products (apart from ethanol) In this question you will be assessed on your written communication skills including the use of specialist scientific terms. [6] 9374 [Turn over *28GCH2205* *28GCH2205*

65 (b) In some countries ethanol is mixed with petrol to make fuels for use in cars. Petrol is mainly octane (C 8 H 18 ), an alkane with 8 carbon atoms. Octane is a hydrocarbon fuel. (i) What is the general formula of the alkanes? (ii) What is meant by the term hydrocarbon? (iii) Write a balanced symbol equation for the complete combustion of octane. [3] 9374 *28GCH2206* *28GCH2206*

66 (c) The diagram below shows a series of organic reactions. A B C A is converted into B by reaction 1 and B is converted into C by reaction 2. (i) Name A, B and C. A B C [3] (ii) Name the substance which reacts with A, in reaction 1, to form B. (iii) Reaction 2 may be carried out using acidified potassium dichromate solution. What colour change would be observed during this reaction? From to (iv) Which one of the substances (A, B or C) would decolourise bromine water? 9374 [Turn over *28GCH2207* *28GCH2207*

67 g of magnesium ribbon reacted with excess dilute hydrochloric acid at room temperature. The volume of gas produced was recorded every 20 seconds. (a) The results obtained in the experiment, using 0.03 g of magnesium ribbon and excess dilute hydrochloric acid, are shown as line C on the graph below C gas volume/cm time/s CCEA 9374 *28GCH2208* *28GCH2208*

68 (i) Use the graph to determine the time taken for the reaction to finish. time taken s (ii) Calculate the rate of this reaction. rate = s 1 [2] 9374 [Turn over *28GCH2209* *28GCH2209*

69 (b) The experiment was repeated using different conditions and the results obtained plotted as lines A, B, D and E on the graph below. Line C shows the original experiment with 0.03 g of magnesium ribbon and excess dilute hydrochloric acid at room temperature E D gas volume/cm C B 10 A time/s CCEA 9374 *28GCH2210* *28GCH2210*

70 (i) State and explain which line, A, B, D or E, was obtained when 0.03 g of magnesium ribbon were replaced by 0.03 g of magnesium powder. Explanation: Line: [2] (ii) Which line, A, B, D or E, was obtained when 0.03 g of magnesium ribbon reacted with excess dilute hydrochloric acid at a temperature below room temperature? Line: (iii) State and explain which line, A, B, D or E, was obtained when g of magnesium ribbon reacted with excess dilute hydrochloric acid at room temperature. Explanation: Line: 9374 [Turn over *28GCH2211* *28GCH2211*

71 (iv) State and explain, in terms of particles, the effect of increasing the concentration of hydrochloric acid on the rate of the reaction between hydrochloric acid and magnesium. Effect: Explanation: [3] 9374 *28GCH2212* *28GCH2212*

72 (c) In an experiment to find a suitable catalyst for a reaction, the following results were obtained. All of the reactions were carried out under the same conditions. Substance under test as a catalyst Time for the reaction to be completed/s cobalt chloride 15 cobalt nitrate 12 potassium nitrate 41 sodium chloride 56 CCEA (i) Which substance in the table is the best catalyst for this reaction? Explain your answer. Substance: Explanation: (ii) A catalyst provides an alternative reaction pathway of lower activation energy. What is meant by the term activation energy? 9374 [Turn over *28GCH2213* *28GCH2213*

73 4 (a) Many gases, for example sulfur dioxide and nitrogen, can be used as refrigerants. (i) Complete the table below about the properties of sulfur dioxide and nitrogen. Property Gas Sulfur dioxide Nitrogen Colour Acidic, basic or neutral neutral [3] (ii) Nitrogen is used as a refrigerant in the food industry because it is unreactive. Explain why nitrogen is unreactive. [2] 9374 *28GCH2214* *28GCH2214*

74 (b) Ammonia gas is also used as a refrigerant. It is used to freeze water in ice rinks. Ammonia is produced in industry by the Haber process which is illustrated in the diagram below. GAS X (from air) GAS Y COMPRESSOR REACTOR CONDENSER AMMONIA Unreacted gases (i) Name the gas X used in the Haber process. (ii) Name the gas Y used in the Haber process. (iii) State the pressure to which the gases are compressed. (iv) Write a balanced symbol equation for the reaction which occurs in the reactor. [3] 9374 [Turn over *28GCH2215* *28GCH2215*

75 (v) Name the catalyst used in the reactor. (vi) State the temperature used in the reactor. (vii) Explain what happens in the condenser. (viii) Suggest why the unreacted gases are recycled. (c) Ammonia can be produced by the reaction of ammonium sulfate with sodium hydroxide. Write a balanced symbol equation for this reaction. [3] 9374 *28GCH2216* *28GCH2216*

76 (d) Water containing dissolved iron(iii) ions is unsuitable for use in an ice rink as the ice formed is coloured. Top Photo Corporation / Top Photo Group / Thinkstock Describe how you would experimentally prove that a sample of this water contained iron(iii) ions. [3] 9374 [Turn over *28GCH2217* *28GCH2217*

77 5 (a) In 1912 Alfred Wegener proposed the theory that the continents on the Earth could move and were once arranged as shown in the diagram below. North America Eurasia South America Africa India Australia Antarctica Dorling Kindersley / Thinkstock Scientists at the time did not accept Wegener s theory, but in the 1960s some new evidence based on the physical properties of iron helped to establish the theory. (i) What name was given to Wegener s theory that the continents could move? (ii) Explain why other scientists at the time did not accept Wegener s theory [Turn over *28GCH2219* *28GCH2219*

78 (b) In the following three reactions, A, B and C, iron is oxidised. Reaction A: Reaction B: Reaction C: iron + oxygen + water hydrated iron(iii) oxide iron + copper(ii) sulfate iron(ii) sulfate + copper iron + hydrochloric acid iron(ii) chloride + hydrogen (i) Write the chemical formula for iron(ii) chloride. (ii) What is the common name for hydrated iron(iii) oxide? (iii) Explain why iron is oxidised in Reaction A. [2] (iv) Describe how you would test for the presence of the hydrogen gas produced in Reaction C. [2] (v) Write a balanced symbol equation for Reaction B. [2] 9374 *28GCH2220* *28GCH2220*

79 (vi) Reaction B is described as a redox reaction. Explain, in terms of electrons, why Reaction B is described as a redox reaction. Your answer should include half equations. In this question you will be assessed on your written communication skills including the use of specialist scientific terms [6] [Turn over *28GCH2221* *28GCH2221*

80 6 Iron is below aluminium in the reactivity series. Iron is extracted from its ore in a Blast Furnace. Aluminium is extracted from its ore by electrolysis. (a) Name the ore from which iron metal is extracted. (b) The extraction of iron in the blast furnace involves three main stages. Stage 1: the production of the reducing agent Stage 2: reduction of iron ore Stage 3: removal of acidic impurities (i) Describe in words the production of the reducing agent in Stage 1. [3] (ii) Write a balanced symbol equation for the reduction of the iron ore in Stage 2. [3] 9374 *28GCH2222* *28GCH2222*

81 (iii) Describe how the acidic impurities are removed. Your answer should include balanced symbol equations. [6] (c) Name the ore of aluminium from which it is extracted. (d) What is meant by the term electrolysis? [2] (e) Write a half equation for the reaction which occurs at the cathode during the extraction of aluminium. [3] 9374 [Turn over *28GCH2223* *28GCH2223*

82 7 Vinegar contains ethanoic acid which is a weak organic acid. (a) A student was asked to determine the concentration of ethanoic acid in a bottle of vinegar. The following procedure was used: 25.0 cm 3 of vinegar solution were measured out and placed in a clean, dry conical flask. A few drops of phenolphthalein indicator were added to the conical flask. A burette was filled with 0.2 mol/dm 3 sodium hydroxide solution. The sodium hydroxide solution was added to the conical flask until the indicator changed colour. (i) Name a suitable piece of apparatus to accurately measure out 25.0 cm 3 of vinegar solution. (ii) Describe in detail how you would prepare and fill the burette for use in this titration. (iii) State the colour change observed at the end-point. From to [2] [4] 9374 *28GCH2224* *28GCH2224*

83 (b) 26.5 cm 3 of sodium hydroxide solution were required to completely react with the vinegar solution in the conical flask. (i) Calculate the number of moles of sodium hydroxide used in the titration. The balanced symbol equation for the reaction is: CH 3 COOH + NaOH CH 3 COONa + H 2 O (ii) Calculate the number of moles of ethanoic acid present in 25.0 cm 3 of the vinegar solution. (iii) Calculate the concentration of the ethanoic acid solution in mol/dm 3. mol/dm 3 (iv) Calculate the concentration of the ethanoic acid solution in g/dm 3. g/dm 3 [2] 9374 [Turn over *28GCH2225* *28GCH2225*

84 (c) A solution of ethanoic acid was prepared by dissolving 12 g of ethanoic acid in 50 cm 3 of deionized water. Calculate the concentration of ethanoic acid in mol/dm 3. mol/dm 3 [3] THIS IS THE END OF THE QUESTION PAPER 9374 *28GCH2226* *28GCH2226*

85 General Certificate of Secondary Education 2015 GCSE Chemistry Unit 2 Higher Tier [GCH22] WEDNESDAY 17 JUNE, MORNING MARK SCHEME F

86 1 (a) (i) water which does not lather readily with soap [2] water which does not lather with soap = AVAILABLE MARKS (ii) deliquescent (iii) temporary hardness removed by boiling permanent hardness is not removed by boiling [2] (b) (i) washing soda (ii) Ca 2+ (aq) + CO 2 3 (aq) CaCO 3 (s) correct formulae of reactants correct formula of product correct state symbols [3] (iii) ion exchange/distillation (iv) tastes better/better for specified health benefi t, e.g. teeth, bones F 3

87 2 (a) Indicative content sugar/glucose (or source of sugar such as fruit) in solution yeast (or zymase) absence of air/anaerobic conditions warm conditions carbon dioxide also produced AVAILABLE MARKS Response Candidates must use appropriate specialist terms to explain fully the process of fermentation (5 6 points of indicative content). They use good spelling, punctuation and grammar and the form and style are of a high standard. Candidates must use appropriate specialist terms to explain fully the process of fermentation (using 3 4 points of indicative content). They use satisfactory spelling, punctuation and grammar and the form and style are of a satisfactory standard. Candidates explain briefl y and partially the process of fermentation (using 2 points of indicative content). They use limited spelling, punctuation and grammar and they have made little use of specialist terms. The form and style are of limited standard. Mark [5] [6] [3] [4] [2] Response not worthy of credit [0] [6] (b) (i) C n H 2n+2 (ii) compound containing only carbon and hydrogen atoms (iii) C 8 H O 2 8CO 2 + 9H 2 O correct formulae of reactants correct formulae of products correct balancing allow multiples [3] (c) (i) A = ethene B = ethanol C = ethanoic acid [3] (ii) steam (iii) orange to green (iv) A F 4