Download Redox Reactions

Redox Reactions
Objectives: define oxidation, define reduction, assign oxidation numbers to all elements
Define Oxidation
-Loss of electrons
-Increase in
oxidation number
Define Reduction
-Gain of electrons
-Decrease in
oxidation number
Rules for Oxidation Numbers
The oxidation number of an uncombined atom is zero
Diatoms included!
The oxidation number of a Group A monatomic ion in a compound is equal to the charge on
the ion
The oxidation number of oxygen in most of its compounds is always –2
Each oxygen in peroxide is -1. Name the compound—unless you say …..
peroxide, oxygen will be -2.
The oxidation number of hydrogen in most of its compounds is +1
When hydrogen is the anion (hydride) it is -1.
The oxidation number of the more electronegative atom in a compound is the same as the
charge it would have if it were an ion
For us, this is NH3. Nitrogen is more electronegative and therefore its
oxidation number is -3. Hydrogen would be +1.
The sum of the oxidation numbers of the atoms in a polyatomic ion is equal to the charge
on the ion
MnO4=-1
x + 4(-2) = -1
x =+7
T. O’Toole
The sum of the oxidation numbers in a neutral compound is zero
CuSO4 = 0
x + (-2) = 0
x =2
Review
What is the oxidation
number of chromium in
K2Cr2O7 ?
Cr2O7 = -2
2x + 7(-2) = -2
2x = +12
x = +6
(1) +12
(2) +2
(3) +3
(4) +6
In which substance does
chlorine have an
oxidation number of +1?
+1 +x +(-2) = 0
x=+1
(1) Cl2
(2) HCl
(3) HClO
(4) HClO2
What is the oxidation
number of chromium in
CrPO4?
x + (-3) = 0
x = +3
(1) +1
(2) +2
(3) +3
(4) +4
Minute Paper
Write the equation and identify the oxidation numbers of all elements for the synthesis of
aluminum bromide.
10 Minute Makeover Customize your learning by choosing from the
following options each night:
 Complete this section on the Portfolio Page
 Review the PPT file on the website
 QUIA practice (http://www.quia.com/jg/1382948list.html)
 Read pages 654-656 in the book
 Extra practice problem: page 656 #9-answer in Appendix C
 Check out the tutorial sources in the LiveBinder
 Complete the SYS Assignment
 Review the skills from today’s Train Your Brain
T. O’Toole