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Redox 3. The Activity Series. Identifying Redox Reactions. Oxidation and reduction occur together When an atom looses one or more electrons (Ox), another atom must gain them (red) Reducing agent – causes reduction to occur Looses one or more electrons Is oxidised
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Redox 3 The Activity Series
Identifying Redox Reactions • Oxidation and reduction occur together • When an atom looses one or more electrons (Ox), another atom must gain them (red) • Reducing agent – causes reduction to occur • Looses one or more electrons • Is oxidised • Oxidising number of atom increases • Metals act as reducing agents • Oxidising agent – causes oxidation to occur • Gains one or more electrons • Is reduced • Oxidation number of atom decreases • Reactive non-metals act as reducing agents
P130 Group 1 metals give up only 1electron to leave M+ group 2 metals usu. give up 2 electrons to leave a dipositive ion (M2+). Transition metals – vary, we work out the oxidation of transition metals by considering the LIGANDS, e.g. Cl in TiCl4 is -1, so Ti must be Ti+4.
Example • Identify the species oxidised, the species reduced, the oxidising agent and reducing agent in the following reaction: • Find the oxidation number of all species present • H • O • Sn Sn • Mn Mn The oxidation number of Mn changes from a +7 to +2, decrease in ox. no. Mn7+ is the species reduced, and MnO4- is the oxidising agent.
Practice exam question • Identify the species oxidised, the species reduced, the oxidising agent and reducing agent in the following reaction • Step 1: determine the oxidation numbers of all species present • Step 2: identify the species which have a change in oxidation number • Step 3: based upon the change in oxidation number, identify the species oxidised, the species reduced and the oxidising and reducing agent.
Additional Problems (p 152) • Where in the periodic table are the best reducing agents found? The best oxidising agents? • Where are the most easily reduced elements found? The most easily oxidised? • Does the substance gain or loose electrons in a redox reaction? • A) an oxidising agent • B) a reducing agent • C) A substance being oxidised • D) a substance undergoing reduction
Assign oxidation numbers to each element: • NO2 SO3 • COCl2 MgH2 • KClO3 NO2- • V2O74- BrO- • Mn2O7 OsO4 • CH2O H2PtCl6