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Redox Reactions.

Redox Reactions. Reduction. Oxidation. Oxidation : Gain of oxygen Loss of electrons. Reduction : Loss of oxygen Gain of electrons. Increase in oxidation number. Decrease in oxidation number. Oxidized – gains oxygen. 2Mg(s ) + O 2 (g)  2MgO(s). Must be a redox!.

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Redox Reactions.

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  1. Redox Reactions. Reduction Oxidation

  2. Oxidation: • Gain of oxygen • Loss of electrons • Reduction: • Loss of oxygen • Gain of electrons Increase in oxidation number Decrease in oxidation number

  3. Oxidized – gains oxygen 2Mg(s) + O2(g)  2MgO(s) Must be a redox! Mg  Mg2+ Oxidized – loss of e- +2e- Put the e- in. O  O2- Reduced – gain of e- +2e-

  4. Cu(s) + 2AgNO3(aq)  Cu(NO3 )2(aq) + 2Ag(s) Complete the half-equations Oxidized? Reduced? Cu  Cu2+ Oxidized – loss of e- +2e- Ag+ Ag Reduced – gain of e- +e-

  5. Summation of the Oxidation Rules • The oxidation number of a free element is zero • Examples of free elements • Gold - Au • Zinc –Zn • The oxidation number of a monatomic ion is equal to its charge • Examples of monatomic ions • Sodium ion - Na+1 • Chloride ion - Cl-1

  6. 3. The sum of the oxidation numbers in the formula of a polyatomic ion is equal to its charge. • Examples of polyatomic ions • Phosphate - PO4-3 • Carbonate - CO3-2 4. The sum of the oxidation number in the formula of a compound is equal to zero • Examples of compounds • Water - H2O • Glucose - C6H12O6

  7. 5. In compounds, Hydrogen has an oxidation number of +1 6. In compounds, Oxygen has an oxidation number of -2 7. In peroxides, oxygen has an oxidation number of -1 • Example of a peroxide • Hydrogen peroxide - H2O2

  8. Oxidation Numbers • The oxidation numbers of atoms in a compound add up to zero. Oxidation state of C in CO2? ? – 4 = 0 ? = +4 Put the +!

  9. Oxidation Numbers • The oxidation numbers of atoms in a compound add up to zero. Oxidation state of Mg in MgCl2? +2

  10. Oxidation Numbers • The oxidation numbers of atoms in an ion add up to the charge on the ion. Oxidation state of S in S2-? -2

  11. Oxidation Numbers • The oxidation numbers of atoms in a compound add up to zero. Oxidation state of N in NH3? -3

  12. Oxidation Numbers • The oxidation numbers of atoms in an ion add up to the charge on the ion. Oxidation state of S in SO42-? ? – 8 = -2 ? = +6

  13. Oxidation Numbers • The oxidation numbers of atoms in an ion add up to the charge on the ion. Oxidation state of N in NH4+? -3

  14. Oxidation: • Gain of oxygen • Loss of electrons • Reduction: • Loss of oxygen • Gain of electrons Increase in oxidation number Decrease in oxidation number

  15. Lets Practice Oxid. # H2SO3 + I2 + H2O → H2SO4 + HI Total Oxid. # FeCl3+ SnCl2 → FeCl2+ SnCl4 Total

  16. Lets Practice Oxid. # AgNO3 + NaClO + AgCl → AgClO3 + NaNO3 Total Oxid. # MnO2+ FeSO4 + H2SO4 → MnSO4 + Fe2(SO4)3 + H2O Total

  17. Lets Practice Oxid. # Mn(NO3)2 + PbO2 + HNO3+ → HMnO4 + Pb(NO3)2 + H2O Total Oxid. # HMnO4 + HNO3 + Mn(NO3)2→ MnSO4 + H2O +O2 Total

  18. Answers to Practice quest 1. +6 2. +3 3. +2 4. +5 5. +5 6. +6 7. +6 8. +1 9. 0 10. +6 11. R= Au O= I R. A.= KI O. A.= AuCl3 12. R= N O= Ag R. A.= Ag O. A.= HNO3 13. R= Fe O= Sn R. A.= SnCl2 O. A.= FeCl3 14. R= N O= Fe, S R. A.= FeS O.A.= HNO3 15.R= Cu O= I R. A.= KI O. A.= CuSO4 16. R= I O= H R.A.= H2 O.A.= KIO3 17. R= Cl O= Cl R.A.= NaClO O. A.= NaClO 18. R= O O= Mn R. A.= MnO2 O. A.= O2 19. R= Mo O= I R. A.= KI O. A.= MoO3 20. R= Br O= Mn R. A.= MnCl2 O. A.= Br2

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