2011 May Chemistry Exam

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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS International General Certificate of Secondary Education

*6145201818*

CHEMISTRY Paper 3 (Extended) Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may use a pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. A copy of the Periodic Table is printed on page 12. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question.

0620/31 May/June 2011 1 hour 15 minutes

For Examiner’s Use 1 2 3 4 5 6 7 8 Total

This document consists of 11 printed pages and 1 blank page. IB11 06_0620_31/4RP © UCLES 2011

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2 1 The following techniques are used to separate mixtures. A simple distillation D chromatography B fractional distillation E filtration C evaporation F diffusion For Examiner’s Use

From this list, choose the most suitable technique to separate the following. (a) methane from a mixture of the gases, methane and ethane .................. (b) water from aqueous magnesium sulfate .................. (c) glycine from a mixture of the amino acids, glycine and lysine ................... (d) iron filings from a mixture of iron filings and water .................. (e) zinc sulfate crystals from aqueous zinc sulfate .................. (f) hexane from a mixture of the liquids, hexane and octane .................. [1] [1] [1] [1] [1] [1] [Total: 6] 2 Selenium and sulfur are in Group VI. They have similar properties. (a) One of the main uses of selenium is in photoelectric cells. These cells can change light into electrical energy. (i) Name a process which can change light into chemical energy. .................................................................................................................................... (ii) Name a device which can change chemical energy into electrical energy. .............................................................................................................................. [2] (b) The electron distribution of a selenium atom is 2 + 8 + 18 + 6. (i) Selenium forms an ionic compound with potassium. Draw a diagram which shows the formula of this ionic compound, the charges on the ions and the arrangement of the valency electrons around the negative ion. Use o to represent an electron from an atom of potassium. Use x to represent an electron from an atom of selenium.

[3]

© UCLES 2011

0620/31/M/J/11

3 (ii) Draw a diagram showing the arrangement of the valency electrons in one molecule of the covalent compound selenium chloride. Use x to represent an electron from an atom of selenium. Use o to represent an electron from an atom of chlorine. For Examiner’s Use

[3] (iii) Predict two differences in the physical properties of these two compounds. .................................................................................................................................... .............................................................................................................................. [2] (c) The selenide ion reacts with water. Se2– + H2O → HSe– + OH– What type of reagent is the selenide ion in this reaction? Give a reason for your choice. ........................................................................................................................................... ..................................................................................................................................... [3] [Total: 13] 3 Iron from the blast furnace is impure. It contains about 4 % carbon and 0.5 % silicon. Most of this impure iron is used to make mild steel, an alloy of iron containing less then...
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