Question

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

Answer 1

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:
`2H^+` + `SO_3^(2-) + Ca^(2+) + 2OH^-` → `SO_3^(2-) + Ca^(2+)` + 2`H_2O`

The net ionic is then:
`2H^+` + `2OH^-` → 2`H_2O`