PJC_H2_CHEM_P3

PIONEER JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION HIGHER 2 CANDIDATE NAME CT INDEX GROUP NUMBER CHEMISTRY 9647/03 Paper 3 Free Response 24 September 2014 2 hours Candidates answer on separate paper. Additional Materials: Answer Paper Graph Paper Data Booklet Cover Page READ THESE INSTRUCTIONS FIRST Write your name, CT group and index number on all work you hand in. Write in dark blue or black pen on both sides of the paper. You may use a soft pencil for any diagrams, graphs or rough workings. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer any four questions. A Data Booklet is provided. You are reminded of the need for good English and clear presentation in your answers. The number of marks is given in brackets [ ] at the end of each question or part question. At then end of the examination, fasten all your work securely together. This document consists of 12 printed pages. 1 3

© PJC 2014 9647/03/JC2 Prelim/2014 2 Answer any four questions. 1 (a) The graph below shows the second and th ird ionisation energies for the first d-block elements scandium to zinc. Ionisation energy / kJ mol 1 By writing relevant electronic configurations, explain why (i) the second ionisation energy of ch romium is higher than that of manganese. (ii) the third ionisation energy of iron is lower than that of manganese. [4] (b) An aqueous solution contains a mixture of iron(III) and zinc ions. (i) Draw a diagram to show the bonding in the hexaaquairon(III) complex ion. (ii) Describe, in a sequence of steps, how you would separate the two cations so that they are obtained as Fe 3+(aq) and Zn2+(aq). Write equations for all the reactions that iron(III) ion and its compound have undergone. You are only provided with HNO3(aq) and NaOH(aq). [5] (c) An aqueous iron( III) solution can be used as a homogeneous catalyst for the reaction between iodide ions and peroxodisulfate ions, S2O8 2. By considering relevant Eo values from the Data Booklet, describe and explain the role of iron( III) ions in the reaction between I and S 2O8 2. Write equations and calculate the Eo cell for the reactions that occur. [4] 2nd IE 3rd IE

© PJC 2014 9647/03/JC2 Prelim/2014 3 (d) The kinetics of the uncatalysed reaction between peroxodisulfate ions and iodide ions can be investigated experimentally. S 2O8 2(aq) + 2I(aq) → 2SO4 2(aq) + I2(aq) To find the rate equation: rate = k[S 2O8 2(aq)]a[I(aq)]b for this reaction, a continuous method with sampling is used. In an experiment, 50.0 cm 3 of 0.200 mol dm 3 of aqueous sodium iodide was mixed with 50.0 cm 3 of 2.00 mol dm 3 aqueous sodium pero xodisulfate. At various time intervals, 10.0 cm 3 of the re