When carbon and oxygen combine chemically, the mass of the product is equal to the total mass of the reactants. This is a fundamental principle in chemistry known as the Law of Conservation of Mass.

Here's why:

* Chemical reactions rearrange atoms, not create or destroy them. When carbon and oxygen react, they form new molecules like carbon dioxide (CO2). The atoms themselves are not lost or gained; they are simply rearranged.

* The mass of each atom remains constant. The mass of a carbon atom before the reaction is the same as its mass after the reaction. The same applies to oxygen atoms.

Therefore, the total mass of the carbon dioxide produced will be exactly the same as the total mass of the carbon and oxygen that reacted.