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SMART LEARNING GURU TUITION CENTRE SECONDARY THREE CHEMISTRY CHAPTER 13 : OXIDATION AND REDUCTION ASSIGNMENT 1 (FUNDAMENTAL QUESTIONS) Name : __________________________( Class : 3 ( 1. ) Grade : ) Date Fill in the blanks in the following table: No Process in terms of 1 Oxygen 2 Hydrogen 3 Electrons transfer 4 Oxidation state / number : ____________ [4] Oxidation Reaction Reduction Reaction 2. For each of the following reaction, identify whether it is an oxidation or reduction reaction, by circling the correct answer. Give a reason for your answer. [12] (a) The conversion of copper to copper (II) oxide. Oxidation / Reduction ________________________________________________________________________ (b) The conversion of ethene, C2H4 to ethane C2H6. Oxidation / Reduction ________________________________________________________________________ (c) The conversion of ammonia to nitrogen. Oxidation / Reduction ________________________________________________________________________ (d) The conversion of sulfur dioxide to sulfur trioxide. Oxidation / Reduction ________________________________________________________________________ (e) The conversion of copper(II) ions to copper. Oxidation / Reduction ________________________________________________________________________ (f) The conversion of bromide ions to bromine molecules. Oxidation / Reduction ________________________________________________________________________ Sec 3 Chemistry 2011 Page 1 of 3 3. Calculate the oxidation number of the following elements. (a) manganese in MnO2 (b) sulfur in H2S (c) vanadium in NH4VO3 (d) chromium in Cr2O72- (e) iron in FeCl3 (f) aluminium in AlF63- 4. (a) (b) [6] IO3- + 5I- + 6H+ 3I2 + 3H2O The reaction of iodate (V) ions with iodide in the presence of acid is shown below. What are oxidation numbers of (i) oxygen in IO3- and (ii) iodine in IO3[2] What changes occurs in the oxidation number of iodine in the reaction, in (i) I- and (ii) IO3-? [2] ________________________________________________________________________ ________________________________________________________________________ (c) Hence, which ion is oxidize? [1] ________________________________________________________________________ 5. Circle the reducing agent in the following reactions. Explain your answers. Sec 3 Chemistry 2011 Page 2 of 3 [4] (a) S + O2 SO2 ________________________________________________________________________ (b) 2Fe + 3Cl2 2FeCl3 ________________________________________________________________________ 6. Circle the oxidising agent in the following reactions. Explain your answers. (a) CuSO4 + Zn ZnSO4 + Cu [4] ________________________________________________________________________ (b) Fe2O3 + 3CO 2Fe + 3CO2 ________________________________________________________________________ 7. Study the following reactions carefully and then identify the reagents that act as oxidizing agents or reducing agents. Write your answers in the table provided. [3] Reaction (a) (b) (c) (a) (b) (c) Oxidising Agent Reducing Agent Aqueous ammonium persulfate, (NH4)2S2O8, is a colourless solution. When aqueous ammonium persulfate is added to aqueous potassium iodide at room temperature, the solution turns yellow and turns brown. When hydrogen peroxide is added to a mixture of potassium dichromate and dilute sulfuric acid, the colour changes from orange to green. When solid sodium nitrite is added to potassium manganate (VII) and dilute sulfuric acid, the solution turns from purple to colourless. Comments from teacher: Sec 3 Chemistry 2011 Page 3 of 3