I’m which chemical equation is the number of atoms in the reactants the same as the number of atoms in the products?
A chemical equation in which the number of atoms of each element in the reactants is the same as the number of atoms of that element in the products is called a balanced chemical equation. Balancing a chemical equation is necessary to satisfy the law of conservation of mass, which states that mass cannot be created or destroyed in a chemical reaction.
For example, consider the simple combustion reaction of methane (CH₄) with oxygen (O₂) to produce carbon dioxide (CO₂) and water (H₂O):
\[ \text{Unbalanced: } CH_4 + O_2 → CO_2 + H_2O \]
Initially, this equation is not balanced. However, when we balance it, we ensure that there are equal numbers of carbon (C), hydrogen (H), and oxygen (O) atoms on both sides. The balanced equation looks like:
\[ \text{Balanced: } CH_4 + 2O_2 → CO_2 + 2H_2O \]
Checking the atom balance:
Reactant side:
- 1 carbon atom (from CH₄)
- 4 hydrogen atoms (from CH₄)
- 4 oxygen atoms (from 2O₂)
Product side:
- 1 carbon atom (from CO₂)
- 4 hydrogen atoms (from 2H₂O)
- 4 oxygen atoms (2 from CO₂ and 2 from 2H₂O)
Since the numbers of each type of atom are equal on both sides of the arrow, this is a balanced chemical equation.