CIE Jun 2016 v3 Paper 2 Q1

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Answer all the questions in the spaces provided. An experiment was carried out to determine the percentage of iron in a sample of iron wire. PMT (a) A 3.35 g piece of the wire was reacted with dilute sulfuric acid, in the absence of air, so that all of the iron atoms were converted to iron(II) ions. The resulting solution was made up to 250 cm3. (i) Write a balanced equation for the reaction between the iron in the wire and the sulfuric acid.[1] A 25.0 cm3 sample of this solution was acidified and titrated with 0.0250 mol dm3 potassium dichromate(VI). 32.0 cm3 of the potassium dichromate(VI) solution was required for complete reaction with the iron(II) ions in the sample. The relevant half-equations are shown. Cr2O7 2 + 14H+ + 6e2Cr3+ + 7H2O Fe2+Fe3+ + e (ii) Use the half-equations to write an equation for the reaction between the iron(II) ions and the acidified dichromate(VI) ions.[1] (iii) Calculate the amount, in moles, of dichromate(VI) ions used in the titration. (iv) Calculate the amount, in moles, of iron(II) ions in the 25.0 cm3 sample of solution. amount =mol [1] (v) Calculate the amount, in moles, of iron in the 3.35 g piece of wire. amount =mol [1] (vi) Calculate the mass of iron in the 3.35 g piece of wire. amount =mol [1]UCLES 2016 9701/23/M/J/16 mass =g [1]<br /> (vii) Calculate the percentage of iron in the iron wire. PMT percentage =% [1] (b) Some electronegativity values are shown. element aluminium chlorine iron electronegativity 1.5 3.0 1.8 (i) Use the data to suggest the nature of the bonding in iron(III) chloride. Explain your answer.[2] (ii) Suggest an equation for the reaction between iron(III) chloride and water.[1] [Total: 10]UCLES 2016 9701/23/M/J/16 [Turn over<br />

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