Final answer:
The balanced chemical equation is achieved when the number of atoms for each element is the same on both the reactant and product sides. For the equation H₂O + CO → CO₂ + H₂, no coefficients are necessary because the equation is already balanced with one molecule of each substance.
Step-by-step explanation:
To balance the chemical equation H₂O + CO → CO₂ + H₂, let's start by considering the number of oxygen atoms on both sides. Initially, there is one oxygen atom in CO and one in H₂O on the reactants side, totaling two oxygen atoms. To balance this with the product side, where CO₂ contains two oxygen atoms, we would need one molecule of CO₂.
This means the coefficient in front of CO₂ must be 1. Next, since we have one molecule of H₂O as a reactant, to balance the hydrogen atoms, we would need one molecule of H₂ on the product side. Therefore, the coefficient for H₂ is also 1. When checking the coefficients for carbon atoms, we see that one CO molecule balances with one CO₂ molecule. At this stage, the balanced equation is 1 H₂O + 1 CO → 1 CO₂ + 1 H₂, but since it is conventional to omit the coefficient '1', the simplified balanced equation is simply H₂O + CO → CO₂ + H₂.