CIE Jun 2014 v2 Paper 4 Q1

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Section A Answer all the questions in the spaces provided. PMT (a) (i) On the diagrams below, show the outer electron arrangements of the atoms and ions indicated. (Use the symbolto represent a pair of electrons in an orbital.) 4s 3d 4s 3d 4s 3d Fe Fe2+(aq) Zn2+(aq) (ii) Use the above diagrams to explain why Fe2+(aq) ions are coloured, whereas Zn2+(aq) ions are colourless.[4] (b) When concentrated HCl is added to a solution of Cu2+(aq) ions, the solution turns yellow. (i) State the formula of the species responsible for the yellow colour and name the type of reaction that has occurred.(ii) Ammonia can react as a base or as a ligand. Describe the colour changes that occur when NH3(aq) is gradually added, with stirring, to the yellow solution, until the NH3(aq) is in excess. Identify the three ions or compounds responsible for the new colours.[7]UCLES 2014 9701/42/M/J/14<br /> PMT (c) When aqueous solutions of KI and K2S2O8 are mixed almost no reaction occurs, but when a few drops of Fe2+(aq) or Fe3+(aq) are added, iodine, I2(aq), is produced at a steady rate. (i) Write an equation for the overall reaction.(ii) State the precise role of the iron ions during this reaction.(iii) By means of equations or otherwise, explain why the presence of either Fe2+ or Fe3+ is able to speed up the reaction.[3] [Total: 14]UCLES 2014 9701/42/M/J/14 [Turn over<br />

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