NITRIC ACID,Concentration/mol dm^-3=0.5 and the pH value=2.0

If you add carbonate to acid you get carbon dioxide. You just need to write down the equation.

Your question doesn't make much sense :confused:

When you add Calcium carbonate, you cannot add until nitric acid is in excess, since as soon as you add the smallest amount of Calcium Carbonate, the nitric will be in excess...