Why do the minerals calcite and dolomite bubble when the mineral or its powder is placed in hydrochloric acid?
1) Both minerals are metal hydrides, and when placed in hydrochloric acid they give off hydrogen gas.
2) Both minerals are sulfides, and the acid reacts to release sulfur dioxide gas.
3) The acid and the mineral together react with oxygen in the air, releasing CO₂ gas.
4) The acid reacts with the mineral to release CO₂ gas that is bound into the crystal as carbonate ion.