Reduction Oxidation I) Reduction Oxidation - called Redox A type of chemical reaction in which electrons are transferred. A chemical reaction in which the charges are changing. If the charges on anything change, then the reaction is redox. You always have both reduction and oxidation. Shortcuts 1) If an element is present, then the reaction is redox. 2) Double replacement is never redox.

- the charge of an element is 0 - the charges in a compound add to 0 Reduction – the charge is reduced by the gain of electrons Oxidation – the charge is increased by the loss of electrons You will need to determine the charge on each element or ion. - the charge of an element is 0 - the charges in a compound add to 0 - the charges of a polyatomic ion add to the total charge - the more electronegative element is negative Charge vs. Oxidation Number

LEO says GER LEO – Losing Electrons is Oxidation GER – Gaining Electrons is Reduction

Reducing agent – the chemical that is oxidized Oxidizing agent – the chemical that is reduced

Al + HCl  AlCl3 + H2 Find the charges on each item. 0 +1 -1 +3 -1 0 0 +1 -1 +3 -1 0 Al + HCl  AlCl3 + H2 What is reduced? (What goes down in charge?) H+1 What is oxidized? (What goes up in charge?) Al What is the reducing agent? (What is oxidized?) What is the oxidizing agent? (What is reduced?)

Write the half reactions. Balance mass and charge. Red: H+1  H2

Write the half reactions. Balance mass and charge. Red: 2 H+1  H2

Write the half reactions. Balance mass and charge. Red: 2 H+1 + 2e-  H2

Ox: Al  Al+3 Write the half reactions. Balance mass and charge. Red: 2 H+1 + 2e-  H2 Ox: Al  Al+3

Write the half reactions. Balance mass and charge. Red: 2 H+1 + 2e-  H2 Ox: Al  Al+3 + 3 e-

The electrons gained must equal the electrons lost. Red: 2 H+1 + 2 e-  H2 Ox: Al  Al+3 + 3 e- The lowest common multiple of 2 and 3 is 6.

Red: (2 H+1 + 2 e  H2) x 3 Ox: (Al  Al+3 + 3 e) x 2 ▼ ▼ Red: 6 H+1 + 6 e  3 H2 Ox: 2 Al  2 Al+3 + 6 e + 2 Al + 6 H+1  3 H2 + 2 Al+3 2 Al + 6 HCl  2 AlCl3 + 3 H2

II) Balancing Redox Reactions Both the mass and charge must be balanced. Steps 1. Find the Charges. 2. Write the Reduction and Oxidation half reactions. 3. Balance the electrons. 4. Combine half reactions. 5. Put coefficients into the original equation. 6. Balance other elements. 7. Balance oxygen using water. Balance hydrogen using H+.