# How do you write a balanced net ionic equation for the reaction of sulfurous acid with calcium hydroxide?

Apr 6, 2016

First write the balanced ionic equation, then retain only those elements that change form.

#### Explanation:

This may be a “thought exercise” because sulfurous acid may not exist in solution, so we are looking at a gas-solid reaction interface.

However, if we simply stick to the “acidity” (hydrogen ions) reacting with the “base” (hydroxide ions) we can make a conjecture of a reaction. Acids and bases react to form salts and water, so the water formation reaction is really the “net” reaction.

H2SO3 + Ca(OH)2 → CaSO3 + 2H2O

in ionic form:
$2 {H}^{+}$ + $S {O}_{3}^{2 -} + C {a}^{2 +} + 2 O {H}^{-}$$S {O}_{3}^{2 -} + C {a}^{2 +}$ + 2${H}_{2} O$

The net ionic is then:
$2 {H}^{+}$ + $2 O {H}^{-}$ → 2${H}_{2} O$