Redox Reactions

REDOX-OXIDATION STATES 16.2-16.3

Day One

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

½ REACTIONS 16.4

Day Two

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 charge5. Balance number of electrons6. Add together the two half reactions & verify

Al(s) + Ag+1 Al+3 + Ag(s)

Fe+2 + MnO4-1 Fe+3 + Mn+2

½ REACTIONS ACIDIC AND BASIC SOLN

Day Three

Balancing Redox Reactionsin Acidic Solutions

1. Split reaction into two ½ reactions 2. Balance all elements except H and O 3. Add electrons to show lose or gain of charge4. Balance number of electrons5. Add Water to balance O 6. Add H+1 to balance H

** NO DIFFERENCE THAN WHAT WE HAVE BEEN DOING!!!!!!!!!!!

HNO3 + H2S S + NO Acidic Solution

Balancing Redox Reactionsin Basic Solutions

1. Split reaction into two ½ reactions 2. Balance all elements except H and O 3. Add electrons to show lose or gain of charge4. Balance number of electrons5. Add Water to balance O 6. 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