1. Introduction to Chemistry
2. The Periodic Table
3. Quantum Numbers
4. Electron Configuration
5. Chemical Families
6. Oxidation Numbers
7. Chemical Formulas
8. Chemical Names
9. Formula Mass
10. Percentage Composition
11. Reaction Types
12. Balancing Equations
13. The Mole Concept
14. Solution Concentration
16. Kinetic Theory
17. The Gas Laws
18. Enthalpy & Heat
19. Reaction Rates
20. Acids & Bases
21. pH Scale
23. Net Ionic Equations
24. Redox Reactions
25. Organic Chemistry
26. Nuclear Chemistry
23. Net Ionic Equations
Net ionic equations attempt to show only the particles involved in a chemical reaction.
A balanced equation in "molecular" form:
2 AgNO3(aq) + ZnCl2(aq) → 2 AgCl(cr) + Zn(NO3)2(aq)
The "net ionic" form of the same equation:
Ag +(aq) + Cl−(aq) → AgCl(cr)
To write net ionic equation, you must first decide - are substances written as molecules or ions?
Molecules or Ions? Seven rules to help decide:
1. Binary acids:
- Strong acids are written in ionic form.
Examples: HCl, HBr, HI
- Weak acids are written in molecular form.
Examples: All other binary acids.
2. Ternary acids:
- Strong ternary acids are written as ions: the number of oxygen atoms exceeds the number of hydrogen atoms by two or more.
Examples: H2SO4, HNO3
- Weak ternary acids are written as molecules.
Examples: H3PO4, HNO2
3. Polyprotic acids:
- Those acids have more than one ionizable hydrogen.
- The second and all other ionizations are always weak.
Examples: H2SO4 is written in ionic form according to Rule #2.
One H is removed leaving HSO4−.
Rule #3 assures us that this particle will not ionize farther.
- Hydroxides of groups 1 and 2, except Be, are strong bases and are written in ionic form.
- All others are weak and written in molecular form.
- Salts are written in molecular form if insoluble.
- Salts are written in ionic form if soluble.
Salt Solubility Rules:
- Salts of group 1 and ammonium (NH4+) are soluble.
- Acetates and nitrates are soluble.
- Binary compounds of group 17, except F, are soluble with metals, except Ag, Hg+, and Pb.
- All sulfates are soluble, except those of Ba, Sr, Pb, Ca, Ag, and Hg+.
- Except for those in Rule 1, carbonates, hydroxides, oxides, sulfides, and phosphates are insoluble.
- Oxides are always written in molecular form.
- Gases are always written in molecular form.
Physical state symbols in an equation can help some with these rules.
For the molecular equation:
H2PO4 (aq) + MnCO3 (s) → Mg3(PO4)2 (cr) + CO2 (g) + H2O (l)
(aq) shows H2PO4 is dissolved in water.
- (s) shows MnCO3 is a solid - insoluble in aqueous solution.
- (cr) shows Mg3(PO4)2 is in crystal form - insoluble in aqueous solution.
- (g) shows CO2 is a gas.
- (l) shows H2O is a liquid.
The net ionic equation is:
H +(aq) + HPO4−(aq) + MnCO3 (s) → Mg3(PO4)2 (cr) + CO2 (g) + H2O (l)
Net Ionic Equations #1
Spectator ions are ions that appear on both sides of the equation.
Steps used to write net ionic equations:
- They are assumed to take no part in the reaction, and are canceled in the process of writing net ionic equations.
- A proper net ionic equation has NO spectator ions in it.
1. Using the 7 rules, write each substance as molecules or ions.
2. Cancel ions that are exactly the same on both sides of the equation.
These ions would cancel: Cu+ → Cu+
3. You must cancel the same number on both sides of the equation.
These ions would not cancel: Cu+ → Cu+2
Before canceling the spectator ions: 4 Fe+2 → 6 Fe+2
4. Cancel any other particles found on both sides of the equation.
After canceling the spectator ions: no iron ions → 2 Fe+2
5. Rewrite the equations in net ionic form.
6. If all coefficients are divisible by a common number, reduced them.
Sample Net Ionic Equation Problem:
Write this molecular equation in net ionic form.
2 AgNO3(aq) + H2SO4(aq) → Ag2SO4(Cr) + 2 HNO3(aq)
See the detailed solution to the problem.
Net Ionic Equations #2
Plating Copper With Zinc
Net Ionic Equations