Oxidation Is often thought of as a combination with oxygen( rusting burning) 2H 2(g) + O 2(g) ----> 2H 2 O (g) CH 4 (g) + 2O > 2H 2 O(g) + CO 2

Reduction Is thought as the removal of oxidation from a compound Examples 2Fe 2 O 3 (s) --> 4Fe(s) + 3O 2 (g) ZnO(s) +C(s)  Zn(s) + CO(g)

Oxidation/Reduction Has a broader definitions and have been recognized to occur at the same time They are complimentary processes

Redox stands for REDuction /Oxidation Oxidation: Loss of electron Reduction: Gain Electrons

How to Remember Redox? As a mnemonic remember LEO says GER Loss of Electrons = Oxidation Gain Electrons = Reduction

What Is Oxidation/Reduction? 2Na(s) + Cl 2 (s) ---> 2NaCl(s) Is this a ReDox Reaction? Why and Why NOT?  Yes  Because Na loss an electron and become Na + ( Na ---> Na + + e -  Cl 2 gained electron and become Cl- (Cl 2 + e - --> 2 Cl-)

Is it possible to oxidize a material without reducing something else? No A lost of electron is taken up by something else

Oxidizing /reducing Agent Reducing agent  Causes reduction by being oxidized itself Oxidation agent  Cause oxidation by being reduced itself 2Na + Cl 2 (g)  2NaCl(s) Which is oxidizing agent? The one reduced  Cl 2 Which is reducing agent? The one oxidized  Na

Recap Loss of Electron = Oxidation Gain of Electrons = Reduction Substance oxidized is the reducing agent Substance reduced is the oxidizing agent Note: Oxidation reduction occurs between metals and nonmetals

Homework #3 p. 602 Identify which is oxidized and reduced a) 6Na (s) + N 2(g) --> 2Na 3 N (s) b) Mg (s) + Cl 2(g) ---> MgCl 2(s) c) 2Al (s) + 3Br 2(l) --> 2AlBr 3(s) d) 4Fe (s) + 3O 2(g) --> 2Fe 2 O 3(s) Ans. Na, N 2 / Mg,Cl 2 / Al, Br 2 / Fe, O 2

How to assign Oxidation States Any element when not combined with atoms of a different element, has an oxidation # of zero( O in O 2 is zero) Any simple monatomic ion has an oxidation number equal to its charge(Na + is +1, O -2 is -2) The sum of the oxidation numbers of all of the atoms in a formula must equal the charge written for the formula.( If the oxidation number of O is -2, then in CO 2 2-, the oxidation # of C is +4. In compounds, the oxidation numbers of IA metals is +1, IIA is +2, IIIA is +3 In Ionic compounds, the oxidation number of a nonmetal or polyatomic ion is equal to the charge of its associated ion. ( CuCl 2, Cl is -1) F is always -1, O is always -2( unless combine with F), H is usually +1

Examples Assign Oxidation states to all atoms in the following molecules or ions a) SO 3 b) SO 4 2- c) N 2 O 5 d) PF3 (6) +[(-2)(3)] (6)+[(-2)(4)] [(5)(2)]+[(-2)(5) (3) +[(-1)(3)] (+6) +(-6) (+6)+(-8) (10)+(-10) (3)+(-3)

Redox between Nonmetals Ex: CH 4 + 2O 2(g) ---> CO 2(g) + 2H 2 O Which one appear to have lost electron? -->Carbon ( from -4 to +4) --> increased oxidation Which one appears to have lost electron? - Oxygen( From 0 to -2) - Reduced oxidation

Practice Identify the following reactions as redox or nonredox and identify the oxidizing/reducing agent PbO (s) + CO (g) --> Pb (s) + CO 2(g) CaCO 3(s) --> CaO (s) + CO 2(g) S (s) +O 2(g) --> SO 2 (g)