OCR A Jun 2012 Paper 1 Q4

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4 Chlorine and its compounds have wide uses in chemistry. 10 (a) In drinking water, HClO kills bacteria. (i) Write an equation to show how HClO can form in drinking water.[1] (ii) Some scientists believe that chlorine compounds should not be present in drinking water. Suggest one reason why scientists may be worried by the presence of these compounds.[1] (b) Chlorine reacts directly with Group 2 elements to form chlorides that are very soluble in water. Aqueous chloride ions can be detected by adding aqueous silver nitrate. The appearance of solid silver chloride, AgCl, confirms the presence of chloride ions. (i) State the type of reaction that has taken place.[1] (ii) Write the ionic equation for this reaction. Include state symbols.[1] (c) A student is given a sample of an unknown Group 2 chloride.The student dissolves 2.86 g of the chloride in water. The student adds excess aqueous silver nitrate. 8.604 g of solid silver chloride, AgCl, forms. (i) Calculate the amount, in moles, of AgCl that forms. The molar mass of AgCl = 143.4 g mol1.OCR 2012 answer =mol [1]<br />
 11 (ii) Deduce the amount, in moles, of the Group 2 chloride that the student dissolves. Hence deduce the relative atomic mass and the identity of the Group 2 metal. Give the relative atomic mass to one decimal place. You must show your working. relative atomic mass =Group 2 metal =[3] (d) Ammonium chloride, NH4Cl, is a salt which has covalent bonding, dative covalent (coordinate) bonding and ionic bonding. (i) What is a dative covalent (coordinate) bond?[1] (ii) Give the formulae of the ions present in NH4Cl.[1] (iii) Draw a dot-and-cross diagram to show the bonding in NH4Cl. Show the outer electrons only. TURN OVER FOR QUESTION 4(e)OCR 2012 [2] Turn over<br />
 (e) A teacher heats potassium chlorate(V), KClO3. The equation is given below. 12 2KClO3(s) 2KCl(s) + 3O2(g) (i) This is an example of a redox reaction. What other type of reaction takes place?[1] (ii) The teacher heats 0.824 g of KClO3. Calculate the volume of oxygen produced, in cm3, measured at room temperature and pressure. Give your answer to the nearest whole number. answer =cm3 [3] [Total: 16] 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 2012<br />

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