2 +1, 2 0 +6 1 +8, 2

see the chart on page 156 for rules about oxidation numbers
you need these so you can tell if you are gaining or losing electrons
reactions are an exchange of electrons. some atoms lose, some atoms gain.
o­2
cl­
Mn+3
reduction ­ is the gaining of electrons ( ­)
oxidation ­ is the losing of electrons ( becoming more +)
Na + SO4 ­
try some!
KClO3
H 2O
UF6
MnO4
reducing agent­ cause another atom to be reduced by donating electrons oxidizing agent­ often oxygen, it is the atom that takes electrons and causes another atom to lose them.
see pg 156 for rules
now try them in a reaction
H2 + O2 = H2O
element = o
ion = charge
oxygen = ­2
hydrogen =1
flourine =­1
last element treat as an ion ( or 1st if need be)
balance 1st so total is zero
if polyatomic ion, balance to charge
+
try some!
Mg +2
KClO3
H 2O
Cl2 (g)
UF6
MnO4
+2
+1, +5, ­2
+1, ­2
0
+6 ­1
+8, ­2
3 ways to look at oxidation­
oxidizing agent
remember that originally oxidation always meant where oxygen had been added, like the creation of rust or tarnishing of silver
Fe + O2 2Fe2O3
figure oxidation states, see what the job of the oxygen is?
so oxidation it also means it is also means to add oxygen
to lose electrons
the increase of oxidation number!!!
it is a good idea to know the chart next page for some common oxidizing and reducing agents!!!
try pg 922 1­11
reduction agent
O2, H2, Halogens F2, Cl 2,I2
halogen ions
F­, Cl­, I­
Cr+3
Cr2O7 ­2
MnO4­
Mn+2
metals, C
quiz over oxidation/reduction numbers
For the following reactions, assign oxidation numbers, then list the oxidizing agent
1. KClO3 KCl + O2
2. H2 + I2 HI
single replacement reactions­ when you have an element and a compound, and the element becomes part of the product compound, oxidation states have altered.
remember net ionic equations? write it out, seperate the ionic compounds, get rid of everything that doesn't change. that is great for redox, cause you can look at just the exchange of electrons
AgNO3 + Cu s CuNO3 + Ags
better yet Ag + + Cus Cu+ + Ags
3. Cu + AgNO3 Ag + CuNO3
activity series
this is a list of metals in order of most reactive to least reactive. it will also help you figure out how a single replacement
reaction should occur. good for oxidation reduction cause that is what most are!
K
Ca
react with water
Na
Mg
Al
Zn
Fe
react with acid
Ni
Sn Pb
H2
Cu
Hg
very unreactive
Ag
Au
F can replace all
I replaces nothing.
so can the following occur?
K + Ca(CO3) KCl + F2
Mg + H20?
Mg + HCl?
Ca + NaOH
Al + ZnS
H2 + KCl
Ca + K2CO3