Untitled - Kelly Walsh High School

Aqueous Solutions 59
Don’t Forget!
lead(II) sulfate solid. One type of equation is the molecular equation in which
both the reactants and products are in the undissociated form:
Pb(NO 3) 2(aq) Na 2SO 4(aq) l PbSO 4(s) 2 NaNO 3(aq)
In a molecular equation, we pretend that everything is a molecule (a nonelectrolyte).
Molecular equations are quite useful when doing reaction stoichiometry
problems.
Showing the strong electrolytes in the form of ions yields the ionic equation
(sometimes called the total or overall ionic equation). The strong electrolytes
are any strong acid, strong base, or water soluble (according to the solubility
rules) ionic compound. In this example, the ionic equation is:
Pb 2 (aq) 2 NO 3 (aq) 2 Na (aq) SO4 2 (aq)
l PbSO 4(s) 2 Na (aq) 2 NO 3 (aq)
Writing the equation in the ionic form shows clearly which species are really
reacting and which are not. In the example above, the Na and NO 3 appear on
both sides of the equation. They do not react, but are simply there in order to
maintain electrical neutrality of the solution. Ions like this, which are not actually
involved in the chemical reaction, are spectator ions.
In writing ionic and net ionic equations, show the chemical species as they actually
exist in solution.
We write the net ionic equation by dropping out the spectator ions and showing
only those chemical species that are actually involved in the chemical
reaction:
Pb2 2 (aq) 2 NO3 (aq ) 2 Na (aq ) SO4 (aq)
l PbSO4(s) 2 Na (aq ) 2 NO3 (aq)
leaving Pb 2 (aq) SO 4 2 (aq) l PbSO4(s)
This net ionic equation focuses on the reactants only. It indicates that an aqueous
solution containing Pb 2 (any solution, not just Pb(NO 3) 2(aq)) will react