If you start with 60 #CaCO_3#'s, how many #CaO#'s will you get?
If we write the balanced chemical equation, will that help you?
Calcium caronate is known to decompose under (fierce) heating to give calcium oxide and carbon dioxide.
To represent this decomposition we write the stoichiometrically balanced equation:
So if I start with
Here I started with 60 formula units of calcium carbonate; at most I can get 60 formula units of calcium oxide. How many formula units of carbon dioxide gas were evolved in this scenario? If you are not satisfied with this answer, voice your objection, and I will give it another go.