Net Ionic Formula

The net ionic equation provides the information of ions that exists in an aqueous medium. Salts get dissolved in polar solvents like water and present as cations and anions in the dissolved state. The net ionic equation indicates the chemical species that undergo a chemical change. The ions that appear on both sides of the equation remain constant and therefore considered to be spectator ions. Many equations have been encountered, most of them have been condensed equations wherein all the reactants and products are indicated as electrically neutral molecules and compounds.

Example 1

Write the net ionic equation that describes the reaction of a weak acid, acetic acid when reacts with an aqueous solution of the strong base strontium hydroxide to form ionic compound strontium and liquid water.

Solution

Ionic equation

2CH₃CO₂H_(aq) + Sr₂⁺_(aq) + 2OH^–_(aq) –> Sr²⁺(aq) + 2CH₃CO₂^–_{(aq) +} 2H2O_(l)

Only strontium is found on both sides of the equation in same form, therefore only strontium can be eliminated from the ionic equation.

2CH₃CO₂H_(aq) + 2OH^–_(aq) –> 2CH₃CO₂^–_(aq) + 2H₂O_(l)

The simplified net ionic equation is,

CH₃CO₂H_(aq) + OH^–_(aq) –> CH₃CO₂^–_(aq) + H₂O_(l)

Example 2

Write the net ionic equation that represents the reaction of aqueous solution of sodium chromate and lead(ll) nitrate which react to form a yellow precipitate of lead(ll) chromate and aqueous solution of sodium nitrate.

Solution

Ionic equation

2Na⁺_(aq) + CrO₄^2-_(aq) + Pb^₂+_(aq) + 2NO₃^–_(aq) –> PbCrO_4(s) + 2Na⁺_(aq) + 2NO₃^–_(aq)

Net ionic equation

CrO₄^2-_(aq) + Pb^₂+_(aq) –> PbCrO_4(s)