Final answer:
The net ionic equation for the reaction between excess hydroiodic acid and calcium sulfite is 2 H+(aq) + SO3^2−(s) → SO2(g) + H2O(l), where hydrogen ions react with sulfite ions to produce sulfur dioxide and water.
Step-by-step explanation:
When excess hydroiodic acid (HI) reacts with calcium sulfite (CaSO3), a net ionic equation can be written by first recognizing the products and the fact that sulfites follow the same solubility trends as sulfates. In an aqueous solution, hydroiodic acid will dissociate completely into hydrogen ions (H+) and iodide ions (I−), while calcium sulfite remains largely undissociated because of its low solubility. The primary reaction that occurs involves the strong acid's hydrogen ions reacting with the sulfite ion to form sulfur dioxide (SO2) and water.
The balanced net ionic equation for the reaction is:
2 H+(aq) + SO32−(s) → SO2(g) + H2O(l)
Notice how we exclude the calcium ion (Ca2+) and the iodide ion (I−) from the net ionic equation as they are spectator ions and do not participate directly in the reaction.