Net Ionic Equation

Most reactions in an aqueous medium involve ions. However, when a reaction takes place two kinds of ions usually emerge: (1) "spectator" ions and (2) "player" ions. The names imply the character of the ions with respect to the reaction. Player ions are directly in the reaction whereas spectator ions fulfill the role of spectators and their primary function is keeping electrical neutrality in the solution. Consider the precipitation reaction that occurs when aqueous solutions of sodium chloride and silver nitrate are mixed. A white precipitate of AgCl forms. The chemical equation for this reaction is written as:

This equation contains all ions in the solution. However, sometimes its necessary to only include those ions that are players and leave out the spectators. A chemical equation that contains only the player ions is called the net ionic equation (nie). To get the nie (1) write out all soluble compounds as ions and (2) eliminate ions common to both reactants and products. The resulting chemical equation is then the nie. For the equation above we have: (for step 2 move the mouse over the reaction)

The resulting equation is the net ionic equation,

While the above reaction is particularly simple (i.e. all stoichiometric coefficients are equal to 1), More complex nie's result from a similar procedure. For example, if iron(III) nitrate is mixed with ammonium sulfide a yellow precipitate of iron(III) sulfide results. The nie for this reaction is:

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C101 Class Notes
Prof. N. De Leon