Cambridge A Level Chemistry 9701 — 2012 May/June Paper 5 · Variant 2

This document consists of 11 printed pages and 1 blank page. DC (AC/SW) 46940/4 © UCLES 2012 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Level * 9 0 3 7 4 1 5 9 2 8 * CHEMISTRY 9701/52 Paper 5 Planning, Analysis and Evaluation May/June 2012 1 hour 15 minutes Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. You may lose marks if you do not show your working or if you do not use appropriate units. Use of a Data Booklet is unnecessary. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 2 Total

2 9701/52/M/J/12 © UCLES 2012 For Examiner’s Use 1 When ammonium nitrate(V), NH4NO3, is heated it decomposes completely into nitrogen(I) oxide, N2O, and water vapour, H2O, which if allowed to cool will condense to liquid water. The stoichiometric equation for this decomposition is NH4NO3(s) → N2O(g) + 2H2O(l). The following information gives some of the hazards associated with ammonium nitrate(V). Ammonium nitrate(V) NH4NO3 Oxidising: Contact with combustible material may cause fire. Explosive when mixed with combustible material. Do not allow the salt to become contaminated with organic matter and do not grind it. You are to plan an experiment to investigate the molar ratio of nitrogen(I) oxide and ammonium nitrate(V) at 25 °C, and confirm that it remains unchanged as the mass of ammonium nitrate(V) changes. (a) (i) Predict quantitatively how the number of moles of nitrogen(I) oxide varies as the number of moles of ammonium nitrate(V) increases, if the products are measured at room temperature 25 °C. … … … … (ii) Predict quantitatively how the sum of the number of moles of water vapour and nitrogen(I) oxide varies as the number of moles of ammonium nitrate(V) increases, if the products are measured at 110 °C. … … … …

3 9701/52/M/J/12 © UCLES 2012 [Turn over For Examiner’s Use (iii) Display both your predictions in the form of sketch graphs on the axes below. Label clearly each axis and each graph line. 0 0 [3]

4 9701/52/M/J/12 © UCLES 2012 For Examiner’s Use (b) In the experiment you are about to plan to test your prediction in (a)(i) at 25 °C, identify the following. (i) the independent variable … (ii) the dependent variable … [2] (c) Draw a diagram of the apparatus and the experimental set up you would use to carry out this experiment. Your apparatus should use only standard items found in a school or college laboratory and show clearly (i) how the solid will be heated, (ii) how the water vapour will be condensed into a liquid and collected. Ice is available, (iii) how the nitrogen(I) oxide will be collected. Label each piece of apparatus used, indicating its size or capacity. [3]

5 9701/52/M/J/12 © UCLES 2012 [Turn over For Examiner’s Use (d) Using the apparatus shown in (c) design a laboratory experiment to test your prediction in (a)(i) for an experiment at 25 °C. In addition to the standard apparatus present in a laboratory you are provided with the following materials. a sample of solid ammonium nitrate(V) crushed ice Give a step-by-step description of how you would carry out the experiment, (i) to produce enough results to give sufficient data to plot a graph as in (a)(iii), (ii) by stating the volumes of nitrogen(I) oxide you would collect, (iii) by calculating the mass of ammonium nitrate(V) needed to produce one of the volumes of nitrogen(I) oxide suggested in (ii), (iv) by stating how you would ensure that decomposition was complete. [Ar : H, 1.0; N, 14.0; O, 16.0; the molar volume of a gas at 25 °C, 24.0 dm3] [4]

6 9701/52/M/J/12 © UCLES 2012 For Examiner’s Use (e) State one hazard that must be considered when planning the experiment and describe a precaution that should be taken to minimise the risk from this hazard. … … … …[1] (f) Draw a table with appropriate headings to show the data you would record when carrying out your experiments and the values you would calculate in order to construct a graph to support or reject your prediction in (a)(i). The headings should include the appropriate units. [2] [Total: 15]

7 9701/52/M/J/12 © UCLES 2012 [Turn over For Examiner’s Use 2 The variation of the volume with pressure of a fixed mass of any ideal gas at constant temperature may be represented by a relationship known as Boyle’s law, PV = constant where P is the pressure of the gas, V is the volume of the gas. A gas such as carbon dioxide, under certain conditions of temperature and pressure, does not always behave as an ideal gas. An experiment was carried out on carbon dioxide to investigate its behaviour. • A calibrated glass tube was filled with a sample of carbon dioxide. • The tube was attached to a calibrated pressure pump. • The pressure and the volume of the gas sample were recorded. • The measured pressure on the gas was increased and the new volume recorded. (a) The results of the experiment are recorded in the table below. A graph of V against P has been plotted for you. Process the results in the table to enable you to plot two further graphs: • PV against P • 1/V against P Record these values to three significant figures in the additional columns of the table. Label the columns you use. For each column you use include units where appropriate and an expression to show how your values are calculated. You may use the column headings A to D for these expressions (e.g. A–B). A B C D pressure of the gas / kPa volume of the gas /cm3 335 9.09 298 10.9 243 13.9 205 17.0 170 20.8 145 24.4 110 27.0 101 35.0 80.0 45.5 60.0 60.0 [2]

8 9701/52/M/J/12 © UCLES 2012 This graph shows the relationship between the volume of the gas and the pressure of the gas. (b) Plot a graph to show the relationship between the product of the pressure and volume, PV, of the gas and the pressure, P, of the gas. Draw the line of best fit. [1] 00 100 200 300 pressure / kPa 400 1000 2000 3000 PV / kPa cm3 4000 00 100 200 300 pressure / kPa 400 10 20 30 volume / cm3 40 50 60

9 9701/52/M/J/12 © UCLES 2012 [Turn over (c) Plot a graph to show the relationship between the reciprocal of the volume of the gas and the pressure (1/V against P) of the gas. Begin the scales on both axes at 0. Draw the line or curve of best fit. [3]

10 9701/52/M/J/12 © UCLES 2012 For Examiner’s Use (d) Circle and label on the graph in (c) any point(s) you consider to be anomalous. For each anomalous point give a different reason why it is anomalous, clearly indicating which point(s) you are describing. … … … … …[2] (e) Determine the initial slope of the graph in (c). Mark clearly on the graph any construction lines and show in your calculation how the intercepts were used in the calculation of the slope. [2] (f) (i) Does the initial shape of your graph in (c) confirm the equation PV = constant? … (ii) Explain your answer in (i) above. … … … … (iii) Why is the graph of volume against pressure provided inappropriate for the verification of Boyle’s law? [3]

11 9701/52/M/J/12 © UCLES 2012 For Examiner’s Use (g) (i) Explain why it was important to measure the initial slope of the graph in (e). … … … (ii) What is the significance of the value of the initial slope? … … …[2] [Total: 15]

12 9701/52/M/J/12 © UCLES 2012 BLANK PAGE Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the May/June 2012 question paper for the guidance of teachers 9701 CHEMISTRY 9701/52 Paper 5 (Planning, Analysis and Evaluation), maximum raw mark 30 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 must be read in conjunction with the question papers and the report on the examination. • Cambridge will not enter into discussions or correspondence in connection with these mark schemes. Cambridge is publishing the mark schemes for the May/June 2012 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 2 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2012 9701 52 © University of Cambridge International Examinations 2012 Question Sections Indicative material Mark 1 (a) PLAN Problem (i) & (ii) States the moles of product increase (as the moles on ammonium nitrate (V)/reactant increases) and the x-axis is labelled moles ammonium nitrate (V)/reactant. Accept proportional or directly proportional for increase. In (ii) it has to be clearly stated that both products are increasing with the increase in ammonium nitrate moles. There are a 1:1 & 1:3 ratios correctly given either in text or in the graph. No curves or plateaus Two lines starting at the origin with moles on the y-axis are correctly labelled with temperature or gas identity and the higher temperature line has a slope greater than that of the other line. No curves or plateaus. [1] [1] [1] (b) PLAN Problem (i) moles of ammonium nitrate. (ii) moles of nitrogen(I) oxide. Accept mass/weight of ammonium nitrate and volume of nitrogen(I) oxide together for one mark. [2] (c) PLAN Method A diagram which shows a heated (closed but with an output tube) piece of apparatus. No water baths or hot plates Showing a condenser and collector for water (e.g. cooled (ice) U-tube) connected to the ammonium nitrate apparatus. If a gas collector is after this piece then the water collector must be gas tight. If no gas collection is attempted after the water condenser then it must be open to air. Allow a Liebig condenser provided it fulfils the same conditions as stated above. Showing a calibrated collecting device accept label syringe/ burette/measuring cylinder as equal to calibrated. To be labelled with size (minimum 10 cm3). To be in train after the water condenser – if a condenser not present – then connected to the heating apparatus. [1] [1] [1]

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2012 9701 52 © University of Cambridge International Examinations 2012 (d) PLAN Method At least five experiments. May be in table (Five+ rows in the table counts as 5 experiments). States intended gas volumes. The range to run as a minimum from x cm3 to 3 times x cm3 where x > = 10 cm3 and maximum volume does not exceed collector capacity. A correct calculation for a mass of ammonium nitrate that will produce one of the gas volumes above. Or a volume from a stated mass. This calculation is not restricted to the capacity of the gas collector. Stopping at a constant volume of gas (not constant mass)/ all solid disappeared/syringe plunger stops moving. Must be an observation not a deduction as – all decomposed or no more gas. [1] [1] [1] [1] (e) PLAN Method Identification of ammonium nitrate as oxidising or explosive (Not NH4NO3 combustible) from the hazcard information and giving a suitable precaution – keeping away from combustible material / wear (chemical) resistant gloves. Accept hot apparatus with heat resistant gloves/tongs. [1] (f) PLAN Method Four columns are required. mass/weight (not amount) of ammonium nitrate (/g); volume of nitrogen(I) oxide (/cm3) (/dm3); number of moles of ammonium nitrate (no unit); number of moles of nitrogen(I) oxide (no unit). The full word for the unit can be used with or without / or (). Four fully correct, two marks; three correct, one mark; otherwise zero. [2] [Total: 15]

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2012 9701 52 © University of Cambridge International Examinations 2012 2 (a) ACE Data The required two column headings PV and (A × B) and /kPacm3 then 1/V and (1/B) and /cm–3 are fully correct. The full word for the unit can be used with or without / or (). All 3 features of the column headings are required. Can accept standard form in the unit only e.g. 3.05 data as /103 kPacm3 or (103 kPacm3). Allow data in standard form. Both columns are fully completed to the correct number of significant figures and all the calculations in each column are correct, (allow two errors). [1] [1] (b) ACE Data Check for a slightly downward sloping continuous curve. No straight/horizontal lines. Ignore the line before the first point and after the last point. [1] (c) ACE Data Label the x-axis pressure and the y-axis 1/volume. Labels can be column headings or unambiguous descriptions with the correct unit in the correct form (/ or ()). The axes must be scaled so that the plotted points must cover at least half the grid in both directions and all points must be on the given grid. A true origin is required on both scales. This mark not available for other plots. Allow subsequent marks for inverted plots. First check any outlying points then check the plotting of points 1, 5, 7, 9 & 10. All 10 points present. Line/curve starting at the origin, accept being straight up from the origin to point 5 (170 kPa) then curving to include the remaining 4 points. Due to differences in plotting, the straight line may extend further and remain correct provided it terminates in a curve and provided it is the line of best fit. [1] [1]* [1]* (d) ACE Evaluation These marks not available for other plots. All the anomalous points are circled on the grid or unambiguously stated in the text. (Selections on the line negate this mark.) (max 5 anomolies) An appropriate explanation gains one mark. Point 7 (1/V high, V low). Volume measured at a lower temperature. For a misplot of low 1/V, accept higher temperature. [1] [1]

Page 5 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2012 9701 52 © University of Cambridge International Examinations 2012 2 (e) ACE Data Two pairs of construction lines on the graph drawn from the line in the initial straight section to the axes and correctly deduces the values of these two intercepts. If the true origin has been used in calculating the slope then only one pair of lines and one intercept is necessary. These construction lines must be in the initial straight section of the plot into the origin and would normally not exceed 170 kPa on x. If the actual plotting and straight line of the candidate exceeds this point a construction that is in the straight line section is correct. No construction lines into curved sections can be used. If the initial straight line is produced onwards then any intercept more than 170 kPa is correct. Allow data from points on the plotted line to be used provided there is some indication on the plot that the point has been used in slope calculation. If the candidate has drawn a straight line rather than a curve then the construction may be anywhere along the line provided the line is drawn into the origin. Do not allow gradients on tangents to a curve unless the curve is at the origin or at x = 0 or y = 0. A correctly calculated value of the slope using the candidate’s figures. Check the candidate’s calculation and correct rounding. The mark is for the magnitude (ignore units). If the candidate used the true origin in the slope calculation then two zeros are not needed in the calculation. Value of slope is around 2.8–2.9 × 10–4. If the slope expression is inverted, then the calculation mark is lost but the intercept value mark can be gained. [1]* [1]* (f) ACE Conclusion These marks not available for other plots. This must relate to the initial shape of their plot. (i) The ‘law’ is justified. AND (ii) In the (initial section of the plot/at lower pressure) the data produce a straight line from the origin. (iii) The graph is a curve or not a straight line. Or the graph has a variable gradient. The best way to verify a relationship is by way of a straight line plot (not a curve). [1] [1] [1]

Page 6 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2012 9701 52 © University of Cambridge International Examinations 2012 (g) ACE Evaluation These marks not available for other plots. Treat these points as the same question (i) This is the area of linearity/straight line/constant gradient. Accept (at low pressures) the gas behaves ideally or (an area) where Boyle’s law is obeyed. (ii) It is the 1/proportionality constant. It’s the value of 1/k. [1] [1] (* is mark available for other plots) [Total: 15]