Question

Why do we know that in the balanced chemical equation $C + {O_2} \to C{O_2}$ , $1g$ of $C$ will not react exactly with $1g$ of ${O_2}$ ?

Answer 1

A chemical equation is a representation of a chemical process in the form of components. A balanced chemical equation is one in which the number of atoms in all of the molecules is equal on both sides of the equation.

Complete answer:
$C$ atoms have a mass unit of $12$ atomic mass units. The weight of an ${O_2}$ molecule is $32$ atomic mass units. As a result, there will be many more carbon atoms in $1$ gram of carbon than there are oxygen molecules in $1$ gram of oxygen.
The balanced equation tells us that a $1$ atom of carbon reacts with exactly one molecule of oxygen, so we can conclude and say that 12g of carbon will react with 32g of oxygen. We can see that this is clearly not the same ratio as $1g$ reacting with $1g$ .

Note:
The balancing of a chemical equation is governed by the law of mass conservation. According to this law, in a chemical reaction, mass cannot be created or destroyed, and the total mass of the elements or molecules present on the reactant side should equal the total mass of the elements or molecules present on the product side.