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Redox Reactions

Redox Reactions. Many practical or everyday examples of redox reactions: Corrosion of iron (rust formation) Forest fire Charcoal grill Natural gas burning Batteries Metabolic processes. combustion. Redox Reactions. There are many different kinds of redox reactions. Combustion

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Redox Reactions

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  1. Redox Reactions • Many practical or everyday examples of redox reactions: • Corrosion of iron (rust formation) • Forest fire • Charcoal grill • Natural gas burning • Batteries • Metabolic processes combustion

  2. Redox Reactions • There are many different kinds of redox reactions. • Combustion CH4 (g) + 2 O2 (g)  CO2 (g) + 2 H2O (g) • Oxidation of Metals by Acids or Metal Salts Cu (s) + H2SO4(aq) CuSO4(aq) + H2(g)

  3. Redox ReactionsOxidation of Metals by Acids or Metal Salts • The reaction between a metal and an acid or between a metal and a metal salt is called a displacementreaction. • a reaction in which an element reacts with a compound and displaces an element from that compound A + BXAX +B

  4. Redox ReactionsOxidation of Metals by Acids or Metal Salts Examples: Mg(s) + 2HCl (aq)MgCl2(aq) + H2(g) Zn(s) + 2 HBr (aq)ZnBr2(aq) + H2(g) Mn (s) + Pb(NO3)2(aq)Mn(NO3)2(aq) + Pb (s)

  5. Redox ReactionsOxidation of Metals by Acids or Metal Salts • How do you know if a redox reaction has occurred? • You must examine the oxidation number of each of the elements present in the reactants and products. • If the oxidation number changes, then a redox reaction has occurred.

  6. Redox ReactionsOxidation of Metals by Acids or Metal Salts • When oxidation occurs: • Electrons are lost • Oxidation number increases • When reduction occurs: • Electrons are gained • Oxidation number is reduced (decreases)

  7. -1 -1 +1 +2 0 0 Oxidation # of Mg increased oxidation Oxidation # of H+ ion reduced reduction Redox ReactionsOxidation of Metals by Acids or Metal Salts Mg(s) + 2HCl (aq)  MgCl2 (aq) + H2 (g)

  8. Redox ReactionsOxidation of Metals by Acids or Metal Salts Example: Identify the element that has been oxidized and the one that has been reduced. Zn (s) + 2 HCl (aq) ZnCl2(aq) + H2(g)

  9. -1 -1 0 +2 0 +1 oxidized reduced Redox ReactionsOxidation of Metals by Acids or Metal Salts • To determine which components have been oxidized and reduced, find the oxidation numbers: Zn (s) + 2 HCl (aq) ZnCl2(aq) + H2(g)

  10. Redox ReactionsOxidation of Metals by Acids or Metal Salts • You can also write a net ionic equation to describe the reaction: • Write all soluble strong electrolytes as ions • Eliminate the spectator ions Zn (s) + 2 HCl (aq) ZnCl2(aq) + H2(g) Zn (s) + 2 H+(aq) + 2 Cl-(aq) Zn2+(aq) + 2 Cl-(aq) + H2(g) Zn (s) + 2H+ (aq) Zn2+ (aq) + H2(g)

  11. Redox ReactionsOxidation of Metals by Acids or Metal Salts Example: Write the complete ionic and net ionic equations for the reaction. Which element is oxidized? 2 Al (s) + 3 Ni(NO3)2(aq) 2 Al(NO3)3 (aq) + 3 Ni (s) 2 Al (s) + 3 Ni2+(aq) + 6 NO3- (aq) 2 Al3+ (aq) + 6 NO3-(aq) + 3 Ni (s) 2 Al (s) + 3 Ni 2+(aq)  2 Al3+ (aq) + 3 Ni (s)

  12. +5 +5 -2 oxidized Redox ReactionsOxidation of Metals by Acids or Metal Salts 2 Al (s) + 3 Ni(NO3)2(aq)2 Al(NO3)3 (aq) + 3 Ni (s) -2 0 +3 0 +2

  13. Redox ReactionsOxidation of Metals by Acids or Metal Salts • Based on the previous equation, we wouldn’t want to store a solution of Ni(NO3)3 in an aluminum container. • The aluminum container would react and dissolve!!! • Metals differ in the ease with which they are oxidized. • Al (s) is oxidized by Ni(NO3)3 (aq) • Ag(s) is NOT oxidized by Ni(NO3)3 (aq)

  14. Redox ReactionsOxidation of Metals by Acids or Metal Salts • Activity series: • A list of metals arranged in order of decreasing ease of oxidation • Used to predict whether a metal will react with an acid or with a metal salt • See table 4.5

  15. Activity Series

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