Edexcel Jun 2010 Paper 1 Q15

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PMT (2) (1) SECTION B Answer ALL the questions. Write your answers in the spaces provided. 15 This question is about the properties of ions and ionic compounds. (a) Solid calcium carbonate, CaCO3, has a giant ionic structure. (i) Draw a diagram (using dots or crosses) for a calcium ion. Show ALL the electrons and the charge on the ion. (ii) Complete the electronic configuration for a calcium ion. 1s2(iii) Would you expect a calcium ion to be bigger, smaller or the same size as a calcium atom? Give TWO reasons to explain your answer. (2)(iv) Explain why ionic compounds have relatively high melting temperatures. (2)*N35691A01128* 11 Turn over<br /> PMT (b) Changes in the concentration of ions in a solution can be estimated by measuring the electrical conductivity of the solution. (i) Explain why solutions of ions are able to conduct electricity. (1)(ii) Suggest why aqueous solutions of calcium chloride, CaCl2(aq), and barium chloride, BaCl2(aq), of the same molar concentration, have different electrical conductivities. (1)(iii) 1 kg of a solution contains 0.100 mol of calcium ions, Ca2+. What is the concentration of the calcium ions by mass in parts per million (ppm)? [Assume the relative atomic mass of calcium is 40.] (2) ppm 12 *N35691A01228*<br /> PMT *(c) Some buildings are made from limestone, which is mainly calcium carbonate. Gases in the atmosphere such as sulfur dioxide, SO2, and nitrogen dioxide, NO2, can be responsible for damaging these buildings. Describe how these gases come to be present in the atmosphere and explain how they can damage a limestone building. (3)(d) The lattice energy of calcium chloride, CaCl2, is 2258 kJ mol1 based on an experimental Born-Haber cycle and 2223 kJ mol1 based on theoretical calculations. Would you expect its bonding to match the ionic model? Justify your answer. (1)(Total for Question 15 = 15 marks) *N35691A01328* 13 Turn over<br />

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