1. Oxidation-reduction reactions
Balancing equations the hard way…

2. What are these reactions?
In a typical double replacement reaction, the ion simply swap partners and there is no change in oxidation number.
In oxidation reactions, electrons are transferred from one atom to another.
Click here for help with oxidation numbers

3. Obvious example 2Na(s)+2H2O(l)2NaOH+H2
In this reaction sodium clearly sheds its outer most electron to from a Na+ ion.
Look, I’ll show you. Click here for a website to show you.

4. Balancing redox reactions
This would take FOREVER to write into a power point so I’m ripping someone else off. They’re good.
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5. Now I’ll show you a couple
Hydrochloric acid is poured onto zinc metal to make zinc chloride and hydrogen gas.
Write the equation

6. Example
Write half reactions

7. Example
Identify oxidizing and reducing agents

8. HNO3(aq)+Cu(s)Cu(NO3)2(aq)+H2O(l)+NO(g)
In acid
Concentrated nitric acid is put on copper wire. Water and copper II nitrate in the water solution is produced, along with a brownish gas, nitrogen monoxide or nitric oxide, NO.
Write the equation
HNO3(aq)+Cu(s)Cu(NO3)2(aq)+H2O(l)+NO(g)

9. HNO3(aq)+Cu(s)Cu(NO3)2(aq)+H2O(l)+NO(g)
Example
HNO3(aq)+Cu(s)Cu(NO3)2(aq)+H2O(l)+NO(g)

10. Example (in acid)
Potassium dichromate and hydrochloric acid in solution will make chlorine gas, water, chromium III chloride and potassium chloride. (The soluble salts, of course, remain in the water solution.)

11. K2Cr2O7 + HCl  KCl + CrCl3 + H2O + Cl2
Example in acid again
K2Cr2O7 + HCl  KCl + CrCl3 + H2O + Cl2

12. Zn+NaNO3+NaOHNa2ZnO2+NH3+H2O
Example in base
Zn+NaNO3+NaOHNa2ZnO2+NH3+H2O