OCR A Jun 2016 Paper 5 Q4

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Iodine, I2, is a grey-black solid that is not very soluble in water. Equilibrium 1 is set up with the equilibrium position well to the left. I2(s) I2(aq) Equilibrium 1 Solid iodine is much more soluble in an aqueous solution of potassium iodide, KI(aq), than in water. Equilibrium 2 is set up. I2(aq) + I(aq) I3 (aq) Equilibrium 2 (a) Suggest why I2 is not very soluble in water.[1] (b) A student dissolves I2 in KI(aq). The resulting 200 cm3 equilibrium mixture contains: 4.00105 mol I2(aq) 9.404102 mol I(aq) 1.96103 mol I3 (aq). Calculate Kc for equilibrium 2. Give your answer to an appropriate number of significant figures.OCR 2016 Kc =units[4]<br />
 (c) The student adds an excess of aqueous silver nitrate, AgNO3(aq), to the equilibrium mixture. Predict what would be observed. Explain the observations in terms of both equilibrium 1 and equilibrium 2 and any species formed.[4] (d) Two redox reactions of iodine are described below. Reaction 1: Iodine is reacted with oxygen to form a compound with a molar mass of 333.8 g mol1. Reaction 2: In alkaline conditions, iodine disproportionates to form iodide ions, iodate(V) ions and water. Construct equations for these two reactions. State symbols are not required. Reaction 1:Reaction 2:[3]OCR 2016 [Total: 12] Turn over<br />

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