You all seemed to have left out the generation of oxygen in this reaction. Oxygen must have been generated as well as carbon dioxide, since the only way the chemical reaction could be balanced involves oxygen:
2Ca(CO)3 + 4CH3COOH --> 2Ca(COCH3)2 + 4CO2 + 2H20 + 3O2
By the way, acetic acid is denoted: HOAc, not HAc; Ac denotes O=CCH3