1. chapter 20 oxidation and reduction another way to balance reactions, or another way to look at what happens during a reaction. reactions are an exchange of electrons. some atoms lose, some atoms gain. reduction - is the gaining of electrons ( -) oxidation - is the losing of electrons ( becoming more +) reducing agent- cause another atom to be reduced by donating electrons oxidizing agent- often oxygen, it is the atom that takes electrons and causes another atom to lose them. see pg 156 for rules

2. see the chart on page 156 for rules about oxidation numbers you need these so you can tell if you are gaining or losing electrons now try them in a reaction H 2 + O 2 = H2O Na + SO 4 - o-2 cl- Mn+3 try some! KClO 3 H2 O UF 6 M nO 4

3. last element treat as an ion ( or 1st if need be) balance 1st so total is zero if polyatomic ion, balance to charge element = o ion = charge oxygen = -2 hydrogen =1 flourine =-1

4. try some! Mg +2 KClO 3 H2 O Cl 2 (g) UF6 MnO4 +2 +1, +5, -2 +1, -2 0 +6 -1 +8, -2

5. 3 ways to look at oxidation- remember that originally oxidation always meant where oxygen had been added, like the creation of rust or tarnishing of silver Fe + O 2 2Fe 2 O 3 figure oxidation states, see what the job of the oxygen is? so oxidation means to add oxygen it also means to lose electrons it is also the increase of oxidation number!!! it is a good idea to know the chart next page for some common oxidizing and reducing agents!!! try pg 922 1-11 +

6. oxidizing agent reduction agent O 2, Halogens F, Cl,I C 2 O 7 -2 M nO 4 - H 2, metals, C

7. quiz over oxidation/reduction numbers For the following reactions, assign oxidation numbers, then list the oxidizing agent 1. KClO 3 KCl + O 2 2. H 2 + I 2 HI 3. Cu + AgNO 3 Ag + CuNO 3

8. what types of reactions are redox reactions? synthesis and decomp. that should make sense since there are elements either as reactants or products single replacement reactions- when you have an element and a compound, and the element becomes part of the product compound, oxidation states have altered. remember net ionic equations? write it out, seperate the ionic compounds, get rid of everything that doesn't change. that is great for redox, cause you can look at just the exchange of electrons AgNO 3 + Cu s CuNO 3 + Ag s be tter yet Ag + + Cu s Cu + + Ag s

9. activity series this is a list of metals in order of most reactive to least reactive. it will also help you figure out how a single replacement reaction should occur. good for oxidation reduction cause that is what most are! K Careact with water Na Mg Al Sn Fereact with acid Ni Sn Pb H 2 C u Hgvery unreactive Ag Au

10. at the same time the list of halogens is just top to bottom of the periodic table. F can replace all I replaces nothing. so can the following occur? Na + Ca(OH) 2 Mg + H 2 0? Mg + HCl?