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Oxidation-Reduction Reactions

Oxidation-Reduction Reactions. Oxidation-Reduction (Redox). Reactions in which electrons are transferred between substances. Use of Oxidation numbers in determining redox reactions is basically a bookkeeping method for keeping track of electrons.

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Oxidation-Reduction Reactions

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  1. Oxidation-Reduction Reactions

  2. Oxidation-Reduction (Redox) Reactions in which electrons are transferred between substances

  3. Use of Oxidation numbers in determining redox reactions is basically a bookkeeping method for keeping track of electrons You must be able to identify an oxidation-reduction reaction. But first, we must learn the rules for assigning oxidation #’s to different species.

  4. Rules for oxidation numbers • Atoms in elemental form are 0. • Cation (positive metal ion); oxidation numbers: Group 1 (+1), Group 2 (+2), Group 13 (+3). • Nonmetals; usually negative numbers. a.) oxygen = -2 unless a peroxide O2-2 then O= -1 b.) Hydrogen +1 with nonmetals, -1 with metals c.) Oxidation numbers: (Group 17) (-1), Group 16 (-2), Group 15 (-3) unless bonded to oxygen then (+) oxidation as in a polyatomic ion (Ex: ClO3-; Cl = +5) 4) Sum of oxidation numbers must = 0 for neutral compound or equal to charge of polyatomic ion. 5) Most electronegative (furthest to right and up) element gets a negative charge.

  5. Atoms in elemental form are 0. • Examples • Ag • Pb • Cl2 • O2 • Oxidation # = 0 for 7 diatomic elements and for all • other elements when by themselves.

  6. Binary Ionic Compounds- • charge of the ion based on Group number. • Examples • AgCl Ag = +1 Cl = -1 • PbI2 Pb = +2 I = -1 • Fe2O3 Fe = +3 O = -2

  7. 3) Nonmetals; usually negative numbers. a.) oxygen = -2 unless a peroxide = -1 b.) Hydrogen +1 with nonmetals, -1 with metals c.) Oxidation numbers: (Group 17) (-1), Group 16 (-2), Group 15 (-3) unless bonded to oxygen then (+) oxidation as in a polyatomic ion (Ex: ClO3-; Cl = +5) Examples PbO oxygen = -2 Na2O2 oxygen = -1 H2S hydrogen = +1 NaH hydrogen = -1 KI iodine = -1 KIO2 iodine = + 3

  8. Determine Oxidation # of element red element in each of the following: MnO2 +4 KMnO4 +7 BrO2- +3 BrO3- +5 Br2 0 HClO4 +7 H2SO4 +6 PO33- +3 CaH2 -1 SO42- +6 Na2S -2 Mg(NO3)2 +5

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