Aqueous Reactions and Net Ionic Equations
I.
Introduction

Double displacement reactions generally take place in _aqueous__ solution.

Aqueous means _a solution in which the solvent is water.

If a substance dissolves, it is soluble.
II. Solubility

Solubility: the ability of one substance to dissolve in another

When ionic compounds dissolve in aqueous solution, they dissociate into their ions: NaCl → Na+ + Cl-
Solubility Rules

Ionic compounds that are soluble will ionize

Ionic compounds that are insoluble will not ionize

If not listed below, assume insoluble
ALWAYS soluble:
group 1
ammonium
acetate
chlorate
nitrate
perchlorate
ALWAYS trumps USUALLY!
USUALLY soluble:
chloride, bromide, iodide, EXCEPT with lead, mercury, or silver
sulfate, EXCEPT with lead, mercury, silver, calcium, barium, or strontium
USUALLY insoluble:
fluoride
phosphate
carbonate
sulfides EXCEPT with Group 2
hydroxides, EXCEPT with groups 1 and 2 (but not magnesium or beryllium)
Ionization Rules

Strong acids ALWAYS ionize

There are seven strong acids: HCl, HBr, HI, HClO3, HClO4, HNO3, H2SO4

Weak acids DO NOT ionize

All acids except the seven listed above are considered weak

Molecular (covalent) compounds DO NOT ionize (even if they are soluble)
Steps to show ionization:
1. Write the formula of the substance.
2. Use the Ionization/Solubility Rules to determine if a substance will ionize when placed in water.
3. If compound will ionize, separate it into the two ions of which it is composed. Subscripts in formula become
coefficients in front of ions.
4. If compound will not ionize, re-write the same formula.
Examples
1. ammonium fluoride
2. lithium sulfide
3. aluminum hydroxide
4. silver sulfate
5. nitrous acid
6. carbon dioxide
7. strontium hydroxide
8. dinitrogen tetroxide
9. sulfuric acid
10. iron (II) sulfide
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III. Aqueous Reactions

These reactions occur “in solution” and must produce one of the products listed below to be considered a valid
reaction.

There are ____3_____ types valid products in aqueous reactions:
1) forms a precipitate (s)
2) forms water (l)
3) forms a gas
 H2(g)
 H2S (g)
 NH4OH = NH3 (g) + H2O (l)
 H2CO3 = CO2 (g) + H2O (l)

Because the H2S exists as a gas, it is called
hydrogen sulfide gas rather than being
named like an acid
Ammonium hydroxide and carbonic acid are
temporary products. They are unstable and
instantly decompose into the products listed.
____Phase__________ symbols are used to represent phases of reactants and products:
aqueous = ___aq______; __reaction where water is present, soluble____
solid = ___s______; __insoluble________________________________
liquid = ____l_____
gas = ___g______
IV. Net Ionic Equations

A complete ionic equation differs from a regular chemical equation (formula equation) in that those substances
that will __dissolve___________ are written as __ions______ in the equation.

____Spectator_______________ _Ion________ are ions that are present on both sides of the equation as ions but
do not actively participate in the VALID reaction.

A net ionic equation only includes the particles that participate in the reaction; the spectators are removed
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Writing Net Ionic Equations:
1) Write and balance the formula equation
2) Write the complete ionic equation
Using ionization/solubility rules, separate all “ionizable” compounds into ions.
3) Cancel out all spectator ions
4) Write the net ionic equation. Re-write remaining species, including appropriate state symbols
If all reactants and products ionize (everything cancels out) write NO REACTION
Examples:
1) sodium sulfate + barium iodide 
2) ammonium chloride + calcium hydroxide 
3) sulfuric acid + potassium hydroxide 
4) magnesium carbonate + nitric acid 
5) copper (II) chlorate + lithium bromide 
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