Section 20.2 lecture for Honors & Prep Chemistry

1. Bellwork- Redox Which species is oxidized? Which one is reduced? What acts as the oxidizing agent? H + (aq) + Li (s)  Li + (aq) + H 2 (g) N 2 (g) + O 2 (g)  2NO 2 (g)

2. Bellwork- Redox Which species is oxidized? Which one is reduced? What acts as the oxidizing agent? H + (aq) + Li (s)  Li + (aq) + H 2 (g) C (s) + O 2 (g)  2CO 2 (g)

3. Cations in compounds or solutions are reduced to elemental metals ex. Na + + e -  Na (s) reduction half-reaction

4. Metals are oxidized into cations ex. Al (s)  Al 3+ + 3e - oxidation half-reaction

5. Combustion reactions are redox reactions. Ex. CH 3 + O 2  CO 2 + H 2 O Carbon & hydrogen are oxidized. Oxygen is reduced.

6. The attachment of oxygen is oxidation. Ex. C becomes part of CO 2 Carbon is oxidized. Oxygen is always reduced.

7. Assign an oxidation number to each atom using the rules: 1. Elements are 0. ex. O 2 (g) , H 2 (g) , Li (s) Monatomic ions are their charge. ex. Na + is +1 and Cl - is -1 2. For compounds Oxygen is -2 Hydrogen is +1 The sum of the oxidation numbers must equal the charge on the compound.

10. An increase in oxidation number is oxidation A reduction in oxidation number is reduction