OXIDATION & REDUCTION REACTIONS
OXIDATION & REDUCTION REACTIONS
CHAPTER 18
REDOX REACTIONS
A reaction in which electrons are transferred from one atom to another is called an oxidation–reduction reaction.
For simplicity, chemists often refer to oxidation–reduction reactions as redox reactions.
OXIDATION NUMBERS
Oxidation numbers refer to the charge value of an element in a compound.
They are used to keep track of electrons.
ASSIGNING OXIDATION NUMBERS
1. The oxidation numbers for any element in their standard state
is zero.
Examples:
C = 0
O2 = 0
S = 0
2. The oxidation number for a monatomic ion is its charge.
Examples:
Ca2+ = 2+
Br- = 1-
MgBr2 = Mg = 2+; Br = 1-
3. The oxidation number of hydrogen is usually 1+. The exception is in a metal hydride where the oxidation number will be 1-.
Examples:
HCl H= 1+
H2SO4 H= 1+
NaH H= 1-
4. Oxygen has an oxidation number of 2- except in H2O2 and Na2O2 then its 1-
5. The sum of the oxidation numbers must be zero in compounds or equal to the charge of the ion.
6. The sum of the oxidation numbers in a polyatomic ion is equal to the charge of the polyatomic ion.
Assign the oxidation state to each element in the following:
(a) K2Cr2O7
(b) MnO4-
(c) Cu2SO3
[pic]
[pic]
[pic]
[pic]
[pic]
Terminology for Redox Reactions
Oxidation:
-Loss of electrons
-Increase in oxidation number
Reduction
-Gaining of electrons
-Decrease in oxidation number
Easy way to remember: LEO the lion says GER
Oxidizing Agent:
-Gets reduced
-Gains electrons
Reducing Agent
-Gets oxidized
-Loses electrons
In a redox reaction the substance that is reduced will gain electrons
This means that its number will be reduced because it is gaining electrons (negatives)
The substance that is being oxidized will loose electrons
This means that its number will go up because it is loosing electrons (negatives)
Identifying the components
[pic]
[pic]
[pic]
Half Reactions
One of the two parts of a redox reaction
Oxidation Half: Produces electrons
Reduction Half: Requires electrons
Balancing Redox Reactions
Use Half Reaction Method
Steps (Acidic)
-Separate equations into half reactions
-Balance elements other than H & O
-Balance O by adding H2O
-Balance H by adding H+
-Balance charge by using electrons
-Multiply equations to make electrons equal
-Add the half reactions
-Simplify
Example
MnO4- + Cl- ( Mn2+ + Cl2
Separate into Half Reactions
[pic]
Balance O by adding H2O & H by adding H+
[pic]
Balance the electrons
[pic]
Balancing Redox Reactions
Multiply oxidation half by 5
Multiply reduction half by 2
Balance the electrons
[pic]
Simplify
[pic]
Steps (Basic)
-Do everything the same as in acid with two additional steps
-Add the same amount of OH- as H+ on both sides
-If the OH- & H+ are on the same side, combine them to make H2O
Example
MnO4- + H2O2 ( MnO2 + O2
Separate into Half Reactions
[pic]
Balance O by adding H2O & H by adding H+
[pic]
Add the same number of OH- as H+ to both sides
[pic]
Combine OH- & H+ on the same side
[pic]
Balance electrons
[pic]
[pic]
Simplify
[pic]
................
................
In order to avoid copyright disputes, this page is only a partial summary.
To fulfill the demand for quickly locating and searching documents.
It is intelligent file search solution for home and business.
Related searches
- oxidation and reduction example
- which identifies an oxidation reduction reaction
- oxidation reduction reaction examples
- oxidation and reduction reactions
- oxidation and reduction reaction
- oxidation reduction reactions quizlet
- oxidation reduction worksheet with answers
- what is an oxidation reduction reaction
- oxidation and reduction reaction calculator
- oxidation reduction worksheet key
- oxidation reduction handout
- oxidation and reduction practice