Download Review of Net-Ionic Equations and Oxidation Numbers–Honors

3 Forms of Chemical
Equations
1) Molecular
 Form you are most familiar with
 Reactants and products written as neutral
compounds
 Ex. KCl + NaF  NaCl + KF
Chemical Equations (cont. )
2) Full Ionic
 All chemical compounds are written as
ions if they can be (ex. Strong
electrolytes, strong acids, strong bases,
etc.)
 Ex. Ba+2 + 2Cl- + 2Na+
BaSO4 (s) + 2Na+ + 2Cl-
+ SO4-2 
How do we write a FULL
IONIC equation?
 Insoluble compounds are written as SOLIDS
 Pure liquids and gases are written as is, not broken up into ions,
electrically neutral.
 Which compounds are broken up into ions????



Soluble ionic compounds
Strong acids (HCl, HBr, HI, HNO3 , HClO4 , H2SO4)
Strong Bases ( Group IA bases and Ca(OH)2, Sr(OH)2 , Ba(OH)2
Forms of Chemical Equations
(cont.)
3) Net Ionic Equations
 Next step after full ionic equation.
 Elimination of Spectator Ions (ions found
on both sides of the equation, not changed
with reaction)
 Includes chemical compounds and ions
DIRECTLY involved in chemical reaction.
Example 1:
Na2CO3 + Ca(NO3)2
Write net ionic equation

2NaNO3 +
CaCO3 (s)
Example 2:
 Magnesium metal reacts with HCL to produce a
solution of magnesium chloride and hydrogen gas.
 Write the molecular equation and net ionic equation.
Oxidation-Reaction???? It’s
more common than you
think……..
Oxidation Numbers/State
 Allows us to identify redox reactions
 A change in these numbers------ REDOX
REACTION ! ! !
 Acts like all chemical compounds are
ionic----gives atom a charge it would have
IF it was ionic
Oxidation Numbers
 No physical meaning
 Assigned to atoms to aid in redox reactions
 Treats all atoms as if they were ions
 ACTUAL charge of monoatomic ions, ASSIGNED
charge to molecular atoms/atoms with a polyatomic
ion
Oxidation Number Rules
 Priority 1st, if there is ANY conflict—go with highest
priority
1) Sum of oxidation numbers = 0 for ALL neutral
compounds (atoms, molecules)
 Any single atoms are also assigned oxidation # = 0
Rule # 1 Examples
 Br2
 MgCl2
 C6H12O6
 Cu
 Ag
 Fe
Oxidation Number Rules
2) Sum of oxidation numbers for an ion = ion’s charge
Examples:
 SO4-2
 NH4+
 Al ion
 Cl ion
Oxidation Number Rules
3) Group 1A metals = +1
Group 2A metals = +2
Examples: MgSO4
K3PO4
Oxidation Number Rules
4) For the majority of chemical compounds—
 F = -1
 H = +1 (sometimes will have -1)
 O = -2
Examples: NH3
H2O
CO
HF
KF
Oxidation Number Rules
5) Group 7A Elements = -1
Group 6A Elements = -2
Group 5A Elements = -3
**When combined with a metal in a binary compound !
Rule #5 Examples
 CaF2
 Li2S
 Mg3N
 K3P
Ex 1. Al2O3
Assign Oxidation Numbers
Ex. 2 K2Cr2O7
Assign Oxidation Numbers
Calculate the oxidation
number of Sulfur in the
following:
1) S8
6) SO2
2) H2S
7) SO3
3) ZnS
8) SO3-2
4) SF4
9) SO4-2
5) SF6
10) H2SO4
Let’s Practice !
 Strategy: assign oxidation numbers you know 1st
1) Cr2O7 -2
2) CaH2
3) KClO4
4) Fe3O4
5) Al2O3
6) K2Cr2O7