Ionic Equations

For strong electrolytes, where the molecules in a reaction completely dissociate to ionic forms in solution, there are two different ways we could think of writing the chemical reaction

• In an example of the neutralization reaction of hydrochloric acid and the metal hydroxide of sodium (i.e. sodium hydroxide) the molecular equation for the reaction would be:

• Since HCl and NaOH are strong electrolytes and will dissociate completely to their ionic forms, we can also write the reaction in terms of a complete ionic equation:

• As with any equation, we can algebraically manipulate the complete ionic equation to cancel the same terms that are present as both reactants and products:

which yields the overall reaction of:

• This is known as the net ionic equation for this particular reaction of strong electrolytes. It has the following characteristics
• The net ionic equation only shows the ions and molecules directly involved in reaction. The other ions (Na⁺ and Cl^- in this case) are called spectator ions (I guess they just sit there and watch and don't get involved).
• Like any reaction, the overall charge on the reactant and products must be equal. In the above case the net charge on the reactants (H⁺ and OH^-) is zero, and the net charge on the product (H₂O) is zero.

Let's look at another neutralization reaction between a strong acid (Nitric acid) and a strong base (KOH):

• The molecular equation would be:

• The complete ionic equation would be:

• The net ionic equation would therefore be:

• This is the same net ionic equation for the reaction of HCl with NaOH

• Only reactions involving soluble, strong electrolytes can be written in ionic form