balnced equation CaCO3-->CaO+CO2

Question

how many moles of CO2 are produced if you start with 3 mol of CaCO3?

Answer 1

The equation tells you that 1 mole CaCO3 = 1 mole CaO = 1 mole CO2; therefore, 3 moles CaCO3 will produce 3 moles of both CaO and CO2.
OR you can use the dimensional approach this way,
3 moles CaCO3 x (1 mole CO2/1 mole CaCO3) = 3 moles CO2. The numbers in the factor within the parentheses come from the balanced equation.