Chemical equations are always balanced because of the law of the conservation of mass, which states that mass cannot be created or destroyed in a chemical reaction. This means that the total mass of the reactants must be equal to the total mass of the products.

In order to balance a chemical equation, coefficients are added to the reactants and products. These coefficients represent the relative numbers of moles of each substance that are involved in the reaction. By adjusting the coefficients, the equation can be made to show that the total mass of the reactants is equal to the total mass of the products.

For example, consider the following unbalanced chemical equation:

$$2H_2 + O_2 → H_2O$$

In this equation, there are two moles of hydrogen gas (H2) on the left side of the equation, but only one mole of water (H2O) on the right side. This means that the equation is not balanced. In order to balance the equation, we need to add a coefficient of 2 to the water molecule:

$$2H_2 + O_2 → 2H_2O$$

Now the equation is balanced because there are two moles of hydrogen atoms on both sides of the equation and two moles of oxygen atoms on both sides of the equation.

Balancing chemical equations is important because it allows us to accurately predict the products of a chemical reaction and to calculate the amount of each product that will be produced.