Classification of Chemical Reactions
Synthesis
Definition
General
formula
Keys to
identity
Subtypes
Examples
Decomposition
Combustion
Other info
Redox?
Classification of Chemical Reactions
Single replacement
Definition
General
formula
Keys to
identity
Subtypes
Double replacement
Examples
Other info
Redox?
Rules for Assigning Oxidation Numbers
RULE
EXAMPLE
1.The oxidation number of any uncombined element is 0.
Na, F2, S8 all = 0
2.The oxidation number of a monatomic ion equals the charge on the ion.
CaCl2, Ca = +2 and Cl = -1
3.The more-electronegative element in a binary compound is assigned
CCl4, Cl = -1, C = +4
the number equal to the charge it would have if it were an ion.
4.The oxidation number of fluorine in a compound is always -1.
HF, F = -1, H = +1
5.Oxygen has an oxidation number of -2 unless it is combined
CaO, O = -2, H2O, O = -2
with F (when it is +2), or it is in a peroxide when it is -1.
6.The oxidation state of hydrogen in most of its compounds is +1
unless it is combined with a metal, in which case it is -1.
OF2, O= +2, H2O2, O= -1
HCl, H = +1, NaH, H = -1
7. The sum of the oxidation numbers of all atoms in a neutral compound is 0
NO, O = -2, so N = +2 because -2 + (+2) = 0
NO2, O= -2, so N = +4 because -2(2) + (+4) = 0
8.The sum of the oxidation numbers of all atoms in a polyatomic
ion equals the charge of the ion.
SO4-2, O = -2 so S = +6 because -2(4) = (+6) = -2
SO3-2, O = -2 so S = +4 because -2(3) = (+4) = -2
For each of the reactions below, assign oxidation numbers to all and identify what has been oxidized and what has been reduced.
4 C5H9O(g) + 27 O2(g) → 20 CO2(g) + 18 H2O(g)
2 Fe(s) + O2 (g) → 2 FeO (s)
2 NH3(aq)+ H2SO4(aq) → (NH4)2SO4(aq)