Chemistry 12 Unit 5. I.Oxidation – Reduction Reactions: Oxidation:A substance losing electrons....
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Transcript of Chemistry 12 Unit 5. I.Oxidation – Reduction Reactions: Oxidation:A substance losing electrons....
Chemistry 12 Unit 5
I. Oxidation – Reduction Reactions:
Oxidation: A substance losing electrons.
Reduction: A substance gaining electrons.
eg: Al(s) in CuCl2(aq)
Al(s) + CuCl2(aq) Cu(s) + AlCl3(aq)(not balanced)
Net Ionic Equation:Al(s) + Cu2+
(aq) Cu(s) + Al3+(aq)
Reduction Half-Reaction:Cu2+
(aq) + 2e- Cu(s)
Oxidation Half-Reaction:Al(s) Al3+
(aq) + 3e-
• The reaction shows that Cu2+ wants electrons more than Al3+
• This type of reaction is called an “oxidation – reduction” reaction or a “redox” reaction.
• Aluminum metal is oxidized and copper (II) ions are reduced.
• The complete redox equation consists of some multiple of the two half-reactions:
Cu2+(aq) + 2e- Cu(s)
Al(s) Al3+(aq) + 3e-
3 ( )
2 ( )
• This shows the same number of electrons gained as lost:
2Al(s) + 3Cu2+(aq) + 6e-
2Al3+(aq) + 3Cu(s) + 6e-
Balanced Redox Equation:2Al(s) + 3Cu2+
(aq) 2Al3+(aq) + 3Cu(s)
• Always check that the total charge on each side of the equation is equal.
2Al(s) + 3Cu2+(aq) 2Al3+
(aq) + 3Cu(s)
3(2+) = 2(3+)
Terminology:
In this example:
Cu2+ is the oxidizing agent.
Al is the reducing agent.
Cu2+ is reduced to Cu.
Al is oxidized to Al3+.
For each of the following, which substance is oxidized and which substance is reduced?
1. Zn + CuSO4 ZnSO4 + Cu
Redox Practice I:
2. CrCl3 + Sn Cr + SnCl4
3. Fe + CuSO4 FeSO4 + Cu
4. MgCl2 + Cr Mg + CrCl3
5. Al + Pb(NO3)2 Al(NO3)3 + Pb
Substance Oxidized
Substance Reduced
For each of the following, which substance is the oxidizing agent and which is the reducing agent?
1. CuSO4 + Zn ZnSO4 + Cu
Redox Practice II:
2. Sn + CrCl3 Cr + SnCl4
3. Fe + CuSO4 FeSO4 + Cu
4. Mg + CrCl3 Cr + MgCl2
5. Al(NO3)3 + Pb Pb(NO3)2 + Al
Oxidizing Agent
Reducing Agent