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Oxidation R eduction Reactions. Electron Transfer Reactions. What type of reactions are Redox reactions?. Combination Reactions A + B AB Decomposition Reactions AB A + B Combustion Reactions C x H y + O2 CO 2 + H 2 O Single Replacement Reactions
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Oxidation Reduction Reactions Electron Transfer Reactions
What type of reactions are Redox reactions? • Combination Reactions • A + B AB • Decomposition Reactions • AB A + B • Combustion Reactions • CxHy + O2 CO2 + H2O • Single Replacement Reactions • A + BC AC + B
What do they all have in common? • One species is losing electrons. That species charge will go up. (oxidation ½ reaction) • Another species is gaining electrons. That species charge is reduced. (reduction ½ reaction) • The species whose charge is increases is the electron donor and therefore the reducing agent. • The species whose charge is decreases is the electron acceptor and therefore the oxidizing agent
How can you tell whose charge is changing? Oxidation states. Simple rules Examples: Find the oxidation state of the underlined atoms. O2 NO3- KMnO4 NaC2H3O2 S2O32- • Elements chg =0 • F-1 • Monatomic ion = chg • O2- (a few exceptions) • IA =+ 1, IIA = +2 • H+1 ( a few exceptions) • In compounds or polyatomic ions the sum of the states = the charge
Now compare them on opposite sides of an equation. • Mg(s) + HCl(aq) Mg2+ +Cl- + H2(g) • Mg goes from 0 to 2+ (oxidation ½ ) • Each H goes from +1 to 0 (Reduction ½ ) • H is gaining 1 electrons and is the agent of oxidation. It oxidized Magnesium • Mg is losing 2 electrons and is the agent of reduction. It reduced hydrogen
Is it balanced?...No • A balanced reaction balanced nuclei and electrons. If 2 electrons are lost 2 must also be gained. Mg(s) + 2HCl(aq) Mg2+ +2Cl- + H2(g)
Balance the following. • Al3+ + Cu Cu2+ + Al • Cl2 + Al Al3+ + Cl- • O2 + H2O + Pb Pb(OH)2 • H+ + MnO4- + Fe2+ Mn2+ + Fe3+ + H2O