OCR A Jan 2012 Paper 1 Q1

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Answer all the questions. This question is about iodine and its compounds. (a) Iodine has a stable isotope with a relative isotopic mass of 127. In 1986, a radioactive isotope of iodine, with a relative isotopic mass of 131, was released into the atmosphere following an explosion at a nuclear power plant in Chernobyl. (i) Define the term relative isotopic mass.[2] (ii) Complete the table to show the number of sub-atomic particles in an atom of iodine-127 and in an atom of iodine-131. protons neutrons electrons iodine-127 iodine-131 53 53 [1] (b) In the human body, iodide ions, I, are necessary for the thyroid gland to function correctly. Some countries add potassium iodide, KI, to table salt as a source of iodide ions. The Guideline Daily Amount, GDA, of iodide ions is 70.0 g (1 g = 1106 g). (i) Calculate the mass of KI, in g, that would be needed to supply the GDA of iodide ions. Give your answer to three significant figures.OCR 2012 answer =g [2]<br /> (i) Write the ionic equation for this reaction.[1] (ii) At room temperature, chlorine is a gas and iodine is a solid. When heated together, chlorine reacts with iodine to form iodine monochloride, ICl. ICl has a higher boiling point than Cl 2. Explain, in terms of the intermolecular forces present, why ICl has a higher boiling point than Cl 2. (ii) Apart from reasons of cost, suggest why some countries do not add KI to table salt.[1] (c) When chlorine gas is bubbled through aqueous potassium iodide, a reaction takes place. In your answer, you should use appropriate technical terms spelled correctly.[2] [Total: 9]OCR 2012 Turn over<br />

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