Download presentation
Presentation is loading. Please wait.
1
REDOX INTRODUCTION
2
What lost e-?s What gained e-? Zn (lost 2-) OXIDATION
Cu2+ (gained 2-) REDUCTION
3
Oxidation-Reduction Reactions
Also known as ‘redox’ reactions. Always occur as a pair (so 2 reactants) LEO the lion says GER OIL (oxidation is loss) RIG (reduction is gain)
4
Example #1 Identify the atoms being oxidized or reduced.
Ag+(aq) + e- Ag(s) Cu(s) Cu2+(aq) + 2 e- 2 Na + Cl2 2 NaCl Write your own example of An oxidation: A reduction: Reduction Oxidation Oxidation of Na Mg(s) Mg 2+(aq) + 2e- F2(g) +2 e- 2F – (aq) Reduction of Cl2
5
Redox Reactions oxidizing agent – causes the other to be oxidized
(itself gets reduced) Which one in this e.g.? Cu2+ (aq) reducing agent – the reactant which caused the other to be reduced (itself gets oxidized) Which one in this e.g.? Zn (s)
6
Example #2 For the following reactions:
Which element is oxidized? reduced? Identify the oxidizing agent. Reducing agent. 2 Ca + O2 2 CaO Mg + Br2 MgBr2 Ca: Reducing agent O2: Oxidizing agent Oxidized Reduced Mg: Reducing agent Br2: Oxidizing agent Oxidized Reduced
7
OXIDATION NUMBERS
8
OXIDATION NUMBERS Oxidation numbers are used to keep track of electrons during reactions. It is an arbitrary system based on: ions charge of an atom electronegativity For any neutral compound, the oxidation numbers of the atoms must add up to zero.
9
compounds containing a single type of atom
OXIDATION NUMBERS Atom or Ion Oxidation Number Examples compounds containing a single type of atom Na Cl2 H in most compounds +1 HCl H in a hydride -1 LiH O in most compounds -2 H2O O in a peroxide H2O2 monatomic ions charge of ion Na+ = +1 S2- = -2
10
Oxidation Numbers General steps to assign oxidation numbers:
Assign common oxidation numbers. use your periodic table The total oxidation number of a molecule or an ion is the value of the charge of the molecule or ion. Unknown oxidation numbers can be assigned algebraically.
11
Example #3 OXIDATION NUMBERS Determine the oxidation numbers for:
MoS2: H2O ClO2-
12
Example #3 OXIDATION NUMBERS Determine the oxidation numbers for:
MoS2: S = 2- from the chart; x + (2 x -2) = total charge = 0 (neutral) x-4 = 0 Mo’s Oxidation No. = 4 H2O ClO2- X + (-2 x 2) =-1 x -4 = -1 x = +3
13
Example #3 OXIDATION NUMBERS SO32- x + 3.(-2) = -2 x = +4 Na3N
H2O x = 0 2x = -2 x= -1 +4 -2 +1 -3 +1 -1
14
Example #3 OXIDATION NUMBERS Determine the oxidation numbers for: MoS2
H2O ClO2- Finding oxidation # of Cl x + 2 x (-2) = -1 x -4 = -1 x =3 +1 -2 +3 -2
15
2 KCl + MnO2 + 2 H2SO4 K2SO4 + MnSO4 + Cl2 + H2O
Example #4 For the following reaction: identify the substance oxidized / reduced oxidizing / reducing agents 2 KCl + MnO2 + 2 H2SO4 K2SO4 + MnSO4 + Cl2 + H2O oxidation +1 -1 +4 -2 +1 +6 -2 +1 +6 -2 +2 +6 -2 +1 -2 reduction i. Cl atoms in KCl are oxidized (-1 to 0). Mn atoms in MnO2 are reduced (+4 to +2) ii. KCl is a reducing agent. MnO2 is the oxidizing agent.
16
HALF REACTIONS
17
HALF REACTIONS All redox reactions may be divided into half-reactions. One half represents the oxidation, while the other is the reduction. Half-reactions are always written for a single mole of a substance. Zn(s) + Cu2+(aq) Zn2+(aq) + Cu(s) Oxidation: Zn(s) Zn2+(aq) + 2e- Reduction: Cu2+(aq) + 2e- Cu(s)
18
HALF REACTIONS Using the half-reactions table, one can predict whether a redox reaction will occur spontaneously. An oxidizing agent (left column) will always spontaneously react with a reducing agent (right column) lower on the list.
19
Yes This table is similar. The higher the voltage, the more reactive the oxidizer.
20
Example #5 HALF REACTIONS
Will iodine be able to oxidize zinc metal to Zn2+ ions? Name an oxidizing agent that can oxidize Br- to Br2, but cannot oxidize Cl- to Cl2. Yes MnO2
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.