Question

When iron metal reacts with sulfuric acid, it produces iron (III) sulfate and hydrogen gas. Balance the equation: Fe + H2SO4 → Fe2(SO4)3 + H2.

Explain why it is necessary to balance chemical equations and why coefficients can be added to an equation, but subscripts cannot be changed.

Answer 1

Conservation of mass - during a chemical reaction, matter is neither created nor destroyed. So on both side of an equation, there needs to be the same atoms in the same number. In order to represent this, we have to balance equations.

You can add coefficients in front of compounds to balance out equations. For example, H2O ---> 2H2O is acceptable. However, you cannot change subscripts, because that would change the identity of the compounds. For example, H2O ---> H2O2 is not acceptable, because we've gone from water to hydrogen peroxide, two different compounds.