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Redox Assign oxidation numbers to reactant and product species. •Define oxidation and reduction. Reduction of Iron Ore •Explain oxidationreduction reactions (redox reactions). Oxidation of Copper Oxidation and reduction reactions: what the gosh darn heck are they? Oxidation: the LOSS of electrons Reduction: the GAIN of electrons Redox LEO the lion says GER! Loss of Electrons is Oxidation. Gain of Electrons is Reduction. OIL RIG Oxidation Is the Loss of electrons. Reduction Is the Gain of electrons. Connection to Electrochemistry • RED CAT • AN OX REDuction occurs at the CAThode. OXidation occurs at the ANode. Half Reactions • Show what happens to electrons in the two parts of a redox reaction: the reduction and the oxidation • Steel hulls in ships have zinc blocks attached because they oxidize and release electrons. These electrons get consumed by the steel and prevent corrosion. Rules for Writing Half-Reactions Equations 1. The number of electrons gained must equal the number of electrons lost. 2. The equation must balance with respect to both atoms and charge. (Charge and mass are conserved in redox equations.) Assigning Oxidation Numbers Write the half-reaction equations for the redox reaction Mg (s) + Br2 (l) → MgBr2 (s) • Step 1: Use oxidation numbers to determine what is oxidized and what is reduced 0 0 2+ 1Mg (s) + Br2 (l) → MgBr2 (s) What happened to Mg? Mg gained a positive charge so it lost electrons. It is oxidized. 0 0 2+ 1Mg (s) + Br2 (l) → MgBr2 (s) What happened to Br2? Br2 got a negative charge so it gained electrons. It is reduced. • Step 2 : Write two separate equations: one showing oxidation and another showing reduction. Use coefficients to balance the number of atoms. Mg → Mg2+ Br2 → 2Br- Step 3: Make the charge balance in each equation by adding electrons. Mg → Mg2+ + 2eBr2 + 2e- → 2Br- Check: 1. The number of electrons gained must equal the number of electrons lost. 2. The equation must balance with respect to both atoms and charge.