Write a net ionic equation for the reaction that occurs when magnesium carbonate (s) and excess hydrochloric acid (aq) are combined.

Answer:
2HBr(aq) + MgS(s) → MgBr2(aq) + H2S(g)
excess
Sulfide ion in solution exists as HS-. Adding additional H+ forces it to H2S gas.
H2S(g) <=> H+(aq) + HS-(aq)