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CIE Jun 2013 v3 Paper 5 Q2
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![Examiners For Use Hydrated iron(II) sulfate can be represented as FeSO4.xH2O where x is the number of molecules of H2O for each FeSO4. When the compound is heated, it loses the molecules of water leaving anhydrous iron(II) sulfate. A suggested equation is: FeSO4.xH2O(s)FeSO4(s) + xH2O(g) An experiment is carried out to attempt to determine the value of x.An open crucible is weighed and the mass recorded. A sample of hydrated iron(II) sulfate is added to the crucible and the new mass recorded. The crucible with hydrated iron(II) sulfate is heated strongly forve minutes and allowed to cool back to room temperature. The crucible with the contents is reweighed and the mass recorded. (a) Calculate the relative formula masses, Mr, of FeSO4 and H2O. [Ar: H, 1.0; O, 16.0; S, 32.1; Fe, 55.8] [1] (b) The results of several of these experiments are recorded below. Process the results in the table to calculate both the number of moles of anhydrous iron(II) sulfate and the number of moles of water. Record these values in the additional columns of the table. You may use some or all of the columns. Masses should be recorded to two decimal places, while the numbers of moles should be recorded to three signi cantgures. 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 G for these expressions (e.g. AB). mass of crucible / g 15.20 15.10 14.95 15.15 15.05 14.90 14.92 15.30 15.07 15.01 mass of crucible + FeSO4.xH2O / g mass of crucible + FeSO4 / g 17.03 17.41 17.33 17.70 17.79 17.88 18.18 18.67 18.64 18.80 16.20 16.41 16.25 16.54 16.55 16.53 16.70 17.14 17.02 17.04UCLES 2013 9701/53/M/J/13 [2]<br />
(c) Plot a graph to show the relationship between the number of moles of anhydrous iron(II) sulfate, FeSO4 (x-axis), and the number of moles of water (y-axis). Draw the line of bestt. It is recommended that you do not include the origin in your choice of scaling.UCLES 2013 9701/53/M/J/13 [3] [Turn over<br />
Examiners For Use 10 (d) Circle and label on the graph any point(s) you consider to be anomalous. For each anomalous point give a different reason why it is anomalous clearly indicating which point you are describing.[3] (e) Determine the slope of the graph. You must mark clearly on the graph any construction lines and show clearly in your calculation how the intercepts were used in the calculation of the slope. [3] (f) Comment on the reliability of the data provided in (b).[1] (g) (i) Use the value of the slope of your graph calculated in (e) to suggest the correct formula for hydrated iron(II) sulfate.(ii) Explain your answer to (i).[2] [Total: 15]UCLES 2013 9701/53/M/J/13<br />](https://learnah.org/wp-content/uploads/2018/08/June_2013_v3_QP_-_Paper_5_CIE_Chemistry_A-level_2-0.jpg)
![Page 4 Mark Scheme GCE A LEVELMay/June 2013 Syllabus 9701 Paper 53 (a) 151.9 AND 18.0 (b) Columns are headed with a label, an expression and units as below. Mol of FeSO4 AND mol of H2O are correct to 3 sig. figs. ECF incorrect Mr. ECF the use of incorrect expressions into data. FeSO4 (CA) / g 1.00 1.31 1.30 1.39 1.50 1.63 1.78 1.84 1.95 2.03 H20 BC / g 0.83 1.00 1.08 1.16 1.24 1.35 1.48 1.53 1.62 1.76 FeSO4 H2O (CA) / 151.9 OR D / 151.9 mol OR mole (BC) / 18 OR E / 18 mol OR mole 0.00658 0.0461 0.00862 0.0556 0.00856 0.0600 0.00915 0.0644 0.00987 0.0689 0.0107 0.0750 0.0117 0.0822 0.0121 0.0850 0.0128 0.0900 0.0134 0.0978 (c) x-axis labelled mol of FeSO4 and y-axis mol H2O AND plotted points cover at least half the grid in both directions. Allow a correct letter from the table as a label. All 10 points plotted correctly. Best fit straight line drawn. 1 1 1 1 1Cambridge International Examinations 2013<br />
Page 5 (d) Mark Scheme GCE A LEVELMay/June 2013 Syllabus 9701 Paper 53 Points 2 and 10 circled. (The circled points must be unambiguously referred to in the reasons.) Point 2 (mass of crucible 15.10) Not all the water had been driven off the iron sulfate crystals OR anhydrous FeSO4 absorbed some water OR has an impurity that does not decompose. Allow water loss is low(er) (than expected). Point 10 (mass of crucible = 15.01) The anhydrous FeSO4 had decomposed OR prior to heating the crucible/original sample was wet and water removed on heating OR contained an impurity which decomposed/was removed on heating. Allow some mass lost (spits out) on heating. 1 1 1 1 1 (e) Appropriately drawn lines on the graph. Correctly read values from the graph. (Figures from the table allowed if no construction lines drawn providing graph drawn does actually go through the points used.) Correctly calculated value of the slope given to 2 or more sig. figs up to calculator value and using the candidates figures AND no units given. (f) Most of the points are on the line OR only a few points are not on the line OR there are only a few anomalies. (g) (i) FeSO4.7H2O (ecf on slope in (e)) (ii) The gradient/slope is the ratio of (moles) of H2O:FeSO4 (is 7 or 7:1). [Total: 15]Cambridge International Examinations 2013<br />](https://learnah.org/wp-content/uploads/2018/08/June_2013_v3_MS_-_Paper_5_CIE_Chemistry_A-level_2-0.jpg)
