Calculate the maximum mass of carbon dioxide that could be obtained by adding excess hydrochloric acid to 15 g of calcium carbonate.

Begin by writing out the reaction.

HCl + CaCO3  →  CaCl2  +  CO2  + H2O

balance the atoms

2HCl + CaCO3  →  CaCl2  +  CO2  + H2O

since CaCO3 is the limiting reagent we must calculate the number of moles of it present.

We do this by dividing the mass of CaCO3 by its molecular mass.

15 / 100 = 0.15 moles.

since the ratio of CaCO3 to CO2 in the reaction above is 1:1.

Then 0.15 moles of CaCO3 can produce a maximum of 0.15 moles of CO2.

To find the mass of 0.15 moles of CO2 we multiply 0.15 by the molecular mass of CO2. 

0.15 x 44 = 6.6g 

Sorry i dont understand the question can you rephase it?