OCR A Jan 2010 Paper 1 Q5

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5 Chemists use the Periodic Table to predict the behaviour of elements. 10 (a) Early attempts at developing a Periodic Table arranged elements in order of increasing atomic mass. (i) State which two elements from the first twenty elements of the modern Periodic Table are not arranged in order of increasing atomic mass.[1] (ii) Why does the modern Periodic Table not arrange some elements, such as those in a(i), in order of increasing atomic mass?[1] (b) Magnesium and strontium are in Group 2 of the Periodic Table. (i) When reacted with oxygen, magnesium forms a white powder called magnesium oxide. Write the equation for the reaction of magnesium with oxygen.[1] (ii) Magnesium reacts with dilute acids. Describe what you would expect to see when magnesium ribbon is added to an excess of dilute hydrochloric acid.[2] (iii) Strontium reacts in a similar way to magnesium. Describe one difference you might observe if strontium, instead of magnesium, was reacted with dilute hydrochloric acid.[1]OCR 2010<br />
 (c) The third period of the Periodic Table features the elements magnesium and chlorine. The table below shows the melting points of these elements. 11 element magnesium chlorine melting point / C 650 101 Describe the structure and bonding shown by these elements. Use your answer to explain the difference in melting points. In your answer, you should use appropriate technical terms spelt correctly.[6] TURN OVER FOR PART (d)OCR 2010 Turn over<br />
 (d) The element strontium forms a nitrate, Sr(NO3)2, which decomposes on heating as shown below. 12 2Sr(NO3)2(s) 2SrO(s) + 4NO2(g) + O2(g) (i) Using oxidation numbers, explain why the reaction involves both oxidation and reduction.[3] (ii) A student heats 5.29 g of Sr(NO3)2 and collects the gas at room temperature and pressure, RTP. 2Sr(NO3)2(s) 2SrO(s) + 4NO2(g) + O2(g) Calculate the volume of gas, in dm3, obtained by the student at RTP. Molar mass of Sr(NO3)2 = 211.6 g mol 1. answer =dm3 [3] [Total: 18] 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, is given to all schools that receive assessment material 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 2010<br />

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