in Chemistry

Use of, and Using Ionic Equations

Molecular Equation

This is sometimes called a balanced equation.

In a molecular equation, all ionic compounds and acids are represented as neutral compounds using the molecular formula. The state of each substance is indicated in parentheses after the formula.

Note the following notations: solid (s), liquid (l), gas (g), or dissolved in water (aq)

Here is an example of a molecular equation:

NaCl (aq) + AgNO3 (aq) → NaNO3 (aq) + AgCL (s)

Here is the above in it’s complete ionic equation:

Na+ (aq) + Cl (aq) + Ag+ (aq) + NO (aq) → Na+ (aq) + NO (aq) + AgCl (s)



 

Na+ (aq) and NO (aq) are present on both sides. These are unchanged, and are called spectator ions.

These can be canceled out, to give our net ionic equation:

Cl (aq) + Ag+ (aq) → AgCl (s)

The net ionic equation tells us that the silver chloride may be produced from dissolved Cl and Ag+ ions, regardless of the source of these ions.

Summary of Ionic Equations

The net ionic equation shows only the chemical species that are involved in a reaction, while the complete ionic equation also includes spectator ions.

We can find the net ionic equation using the following steps:

  1. Write a balanced molecular equation, including the state of each substance
  2. Use your knowledge of solubility rules, strong acids, and strong bases to rewrite the equation as the complete ionic equation showing which compounds are dissociated into ions
  3. Cancel out the spectator ions that appear on both sides of the equation to get the net ionic equation


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