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Redox Reactions Day One REDOX-OXIDATION STATES 16.2-16.3 Oxidation-Reduction • Process of gaining or losing electrons • Oxidation: losing electrons • Reduction: Gaining Electrons OIL RIG How do we Identify if something is being reduced or oxidized? • Oxidation States (Oxidation Numbers) – Computed for each element based on the number of electrons assigned • There are FIVE (5) Rules for assigning Oxidation States Oxidation State RULES 1. Oxidation state of an atom in a free element is ZERO (0). 2. Hydrogen always has an oxidation number of (+1) , except in hydrides 3. Oxygen always has an oxidation number of (-2), except in peroxides Oxidation State Rules 4. The sum of oxidation states of all atoms in: – Molecule = (0) – Ion = charge of the ion 5. In their compounds, – Group I metal = (+1) – Group II metals (+2) LETS TRY A FEW!!! • • • • • • Br2 K+1 LiF CO2 SO4-2 Na2O2 Br = 0, Br= 0 1+ Li = 1+, F = 1- total = 0 O = -2 each = -4 Total = 0 C = +4 O= -2 ea. = -8 S = +6 Total = -2 Na = +1ea. = +2 O = -2 ea. = -4 Na has priority so it sets the rule so O will have a -1ea so the total = 0 Identify Redox Reaction • You can identify a redox by checking to see if one compound was reduced and the other was oxidized. • Remember: – Oxidation = an increase in oxidation state – Reduction = a decrease in oxidation state Day Two ½ REACTIONS 16.4 Balancing Redox Reactions 1. Assign Oxidation Numbers 2. Split reaction into two ½ reactions 3. Balance all elements except H and O - balance O by adding H2O - balance H by adding H+1 4. Add electrons to show lose or gain of charge 5. Balance number of electrons 6. Add together the two half reactions & verify Al(s) + Ag+1 Al+3 + Ag(s) Fe+2 + MnO4-1 Fe+3 + Mn+2 Day Three ½ REACTIONS ACIDIC AND BASIC SOLN Balancing Redox Reactions in Acidic Solutions 1. 2. 3. 4. 5. 6. Split reaction into two ½ reactions Balance all elements except H and O Add electrons to show lose or gain of charge Balance number of electrons Add Water to balance O Add H+1 to balance H ** NO DIFFERENCE THAN WHAT WE HAVE BEEN DOING!!!!!!!!!!! HNO3 + H2S S + NO Acidic Solution Balancing Redox Reactions in Basic Solutions 1. 2. 3. 4. 5. 6. Split reaction into two ½ reactions Balance all elements except H and O Add electrons to show lose or gain of charge Balance number of electrons Add Water to balance O Add H+1 to balance H 7. Neutralize H+1 by adding the appropriate amount of OH-1 to EACH SIDE NO2 NO-2 + NO3-1 Basic Soln