Final answer:
Calcium sulfide reacts with hydroiodic acid to form calcium iodide and hydrogen sulfide gas. The reaction is a typical acid-base interaction, resulting in the formation of a halide salt and a gas.
Step-by-step explanation:
When calcium sulfide (CaS) reacts with hydroiodic acid (HI), the predicted reaction produces calcium iodide (CaI2) and hydrogen sulfide gas (H2S). The balanced chemical equation for this reaction is:
CaS (s) + 2HI (aq) → CaI2 (aq) + H2S (g)
This reaction is consistent with the general behavior where hydroxides, carbonates, and some oxides react with solutions of the hydrogen halides to form halide salts and corresponding other products. In this case, calcium sulfide which is an ionic compound interacts with hydroiodic acid to form an aqueous solution of the iodide salt and releases hydrogen sulfide gas as a byproduct. It’s a typical acid-base reaction where the sulfide ion acts as a base, and HI behaves as an acid.