Hints for Net Ionic Equations

Hints for Net Ionic Equations

Directions as given in the Advanced Placement Exam:

Give the formulas to show the reactants and the products for FIVE of the following chemical reactions. Each of the reactions occurs in aqueous solution unless otherwise indicated. Represent substances in solution as ions if the substance is extensively ionized. Omit formulas for any ions or molecules that are unchanged by the reaction. In all cases a reaction occurs. You need not balance.

1. Review the formulas of common ions and their charges. No credit is given for incorrect formulas.

2. Write formulas of ions with charges; solids, gases, and molecular substances are written as neutral substances. No credit is given for species with incorrect charges.

3. Review the solubility rules.

4. Know the strong acids. These are 100% ionized in water; other acids are molecular.

5. Try to classify the type of reaction: acid-base, redox, complex formation, precipitation, etc. (also: combination, decomposition, single replacement, double replacement)

6. When a free element is involved, look for a redox reaction. In all redox reactions you must have both an oxidized and a reduced substance.

7. Learn to recognize some common oxidizing agents (they are your clue for redox) and to predict their products.

8. Nonmetallic oxides plus water form acids; metallic oxides plus water form bases. The nonmetal or metal keep the same oxidation number. Nonmetallic oxides plus bases form a salt plus water. Metallic oxides plus acids form a salt plus water. Nonmetallic oxides plus metallic oxides form a salt. Think of nonmetallic oxides as "acid formers" and metal oxides as "base formers."

9. Amphoteric ions such as Zn2+ and Al3+ form hydroxides that dissolve both acid and base. In base you may find the complex ions Zn(OH)42-, Al(OH)4-, or Al(OH)63-.

10. Ammonia forms complex ions such as Ag(NH3)2+. Cu(NH3)42+, Zn(NH3)4 2+. These are broken up by the addition of acid. This changes NH3 to NH4+.

11. Even if you don’t know products, write down a formula for the reactants. If you are not sure of the formula of one product, write down the formula for the other product. Partial credit!

12. It is not necessary to include symbols for the substance‘s state (solid, liquid, gas, aqueous).

13. Do not include spectator ions. Do not take the time to balance, but all elements must be accounted for on both sides of the arrow.