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CIE Mar 2016 v2 Paper 2 Q2
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![Spathose is an iron ore that contains iron(II) carbonate, FeCO3. The percentage of iron(II) carbonate in spathose can be determined by titration with acidified potassium dichromate(VI) solution using a suitable indicator. PMT The ionic equation is shown below. Cr2O7 2(aq) + 14H+(aq) + 6Fe2+(aq)2Cr3+(aq) + 6Fe3+(aq) + 7H2O(l) (a) A 5.00 g sample of spathose was reacted with excess concentrated hydrochloric acid and then filtered. The filtrate was made up to 250 cm3 in a volumetric flask with distilled water. A 25.0 cm3 sample of the standard solution required 27.30 cm3 of 0.0200 mol dm3 dichromate(VI) solution for complete reaction. (i) Calculate the amount, in moles, of dichromate(VI) ions used in the titration. (ii) Use your answer to (i) to calculate the amount, in moles, of Fe2+ present in the 25.0 cm3 sample. amount =mol [1] (iii) Use your answer to (ii) to calculate the amount, in moles, of Fe2+ present in the 250 cm3 volumetric flask. amount =mol [1] (iv) Use your answer to (iii) to calculate the mass of iron(II) carbonate present in the sample of spathose. amount =mol [1] (v) Calculate the percentage of iron(II) carbonate in the sample of spathose. mass =g [2] percentage of iron(II) carbonate =% [1]UCLES 2016 9701/22/F/M/16<br />
PMT (b) Iron ores containing iron(III) compounds can be analysed using a similar method. A standard solution of an aqueous iron(III) compound is reacted with aqueous tin(II) chloride. Aqueous tin(IV) chloride and aqueous iron(II) chloride are the products of this reaction. (i) Write an ionic equation for this reaction. Do not include state symbols.[2] (ii) Any excess tin(II) chloride can be removed by reaction with HgCl 2(aq). A white precipitate of Hg2Cl 2 is produced. Complete the equation for this reaction. () + HgCl 2(aq)SnCl 4() + Hg2Cl 2() [2] [Total: 10]UCLES 2016 9701/22/F/M/16 [Turn over<br />](https://learnah.org/wp-content/uploads/2018/08/March_2016_v2_QP_-_Paper_2_CIE_Chemistry_A-level_2-0.jpg)
![Page 2 Mark Scheme Syllabus Paper Cambridge International AS/A LevelMarch 2016 9701 22 PMT Answer Mark Total Question (a) (i) greater attractive force OR greater force between nucleus and (outer) electrons proton number / atomic number / nuclear charge increases across period AND electrons occupy same shell / shielding roughly constant (ii) sulfurs electron removed from full (3p) orbital OR sulfur has two electrons in the same orbital electronelectron repulsion (reduces energy required) (iii) sodium has mobile / free electrons / electrons free (to move throughout the structure) phosphorus is simple / covalent / molecular (iv) magnesium has two free / delocalised / outer / valence electrons per atom OR more free / delocalised / outer electrons than sodium (b) (i) A = Mg(NO3)2 B = H2 C = NO2 OR O2 D = O2 OR NO2 [1] [1] [1] [1] [1] [1] [1] [1] [1] [1] [1] [2] [2] [2] [1] [4] (ii) any Group I carbonate OR ammonium carbonate [1] [1] (a) (i) 27.30 10000.020 =5.4610 4(mol) (ii) (i)6 =3.2810 3(mol) [12] [1] [1] [1] [1]Cambridge International Examinations 2016<br />
Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A LevelMarch 2016 9701 22 PMT Answer Mark Total [1] [1] [2] [1] [2] [2] [10] [3] [1] [1] [1] [1] [1] [1] [1] [1] [1] [1] Question (iii) (ii)=3.2810 250 25.00 2(mol) (iv) r of FeCO3 =55.8 + 12.0 + 3(16.0) = 115.8 (v) (iii)M r(FeCO3) =3.79 g (iv) 5.00 100% = 75.9% (b) (i) 2Fe + Sn2Fe + Sn 3+ 2+ 2+ 4+ species balancing (ii) SnCl 2(aq) + 2HgCl 2(aq) SnCl 4(aq) + Hg2Cl 2(s) SnCl 2 AND 2 state symbols (a) (i) three bonding pairs lone pair AND octet shape = (trigonal) pyramidalCambridge International Examinations 2016<br />](https://learnah.org/wp-content/uploads/2018/08/March_2016_v2_MS_-_Paper_2_CIE_Chemistry_A-level_2-0.jpg)
