OCR A Jan 2011 Paper 1 Q5

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5 Chlorine, bromine and iodine are halogens commonly used in school and college experiments. 10 (a) Halogens have van der Waals forces between their molecules. (i) Describe how van der Waals forces arise.[3] (ii) State and explain the trend in the boiling points of chlorine, bromine and iodine.[3] (b) The halogen astatine does not exist in large enough quantities to observe any of its reactions. Why would astatine be expected to react similarly to other halogens?[1]OCR 2011<br />
 (c) A student investigated the reactivity of halogens by attempting some redox reactions. 11 (i) The student added bromine water to aqueous solutions of sodium chloride and sodium iodide in separate test-tubes. The student then added an organic solvent, cyclohexane, to each test-tube and these were shaken. State what colour you would see in the cyclohexane in each test-tube after shaking.Write ionic equations for any chemical reactions that take place.State and explain the trend in reactivity shown by these observations. In your answer you should use appropriate technical terms spelled correctly.[6] (ii) Suggest why the student carried out the reactions in a well ventilated area.[1]OCR 2011 Turn over<br />
 12 (d) The halogen fluorine is too reactive to use in a school or college laboratory. Fluorine is a powerful oxidising agent. It will react with water as shown below. (i) Complete and balance the equation for the reaction of fluorine with water. F2(g) + H2O(l)+ O2(g) [1] (ii) Using oxidation numbers, show what has been oxidised and what has been reduced in this reaction.[2] (e) Fluorine will react violently with gallium to produce gallium fluoride. Mendeleev originally called gallium eka-aluminium as he predicted that gallium would have similar properties to aluminium. (i) Complete the electron structure of the gallium atom. 1s2[1] (ii) Use Mendeleevs prediction to suggest the empirical formula of gallium fluoride.[1] [Total: 19] END OF QUESTION PAPER Copyright Information OCR is committed to seeking permission to reproduce all third-party content that it uses in its assessment materials. OCR has attempted to identify and contact all copyright holders whose work is used in this paper. To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced in the OCR Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download from our public website (www.ocr.org.uk) after the live examination series. If OCR has unwittingly failed to correctly acknowledge or clear any third-party content in this assessment material, OCR will be happy to correct its mistake at the earliest possible opportunity. For queries or further information please contact the Copyright Team, First Floor, 9 Hills Road, Cambridge CB2 1GE. OCR is part of the Cambridge Assessment Group; Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.OCR 2011<br />

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