The gas carbon dioxide is released.
Magnesium chloride is formed.
Carbon Dioxide
The gas released in the reaction of calcium carbonate with hydrochloric acid is carbon dioxide. CaCO3 + 2 HCl = CaCl2 + CO2 + H2O
The products that are formed will be magnesium salt, water and carbon dioxide. Exactly what salt is made depends the acid used. Hydrochloric acid produces magnesium chloride; sulphuric acid produces magnesium sulphate; nitric acid produces magnesium nitrate.
This is a complicated titration problem. The volumes are necessary to solve the problem, as well as a Ka or Kb value.
magnesium chloride? LOL
Calcium carbonate is a base and hydrochloric acid is an acid but their combined pH depends on ther initial concentrations.
Carbon Dioxide
Carbon Dioxide
Sodium chloride
It's a chemical reaction.
Limescale is mostly calcium carbonate with some magnesium carbonate mixed in there as well. So the answer would be calcium.