A chemical equation describes what happens in a chemical reaction. The equation identifies the reactants (starting materials) and products (resulting substance), the formulas of the participants, the phases of the participants (solid, liquid, gas), and the amount of each substance. Balancing a chemical equation refers to establishing the mathematical relationship between the quantity of reactants and products. The quantities are expressed as grams or moles.
It takes practice to be able to write balanced equations. There are essentially three steps to the process:
- Write the unbalanced equation.
Products are listed on the righthand side of the equation.
Reactants and products are separated by putting an arrow between them to show the direction of the reaction. Reactions at equilibrium will have arrows facing both directions.
- Balance the equation.
Once one element is balanced, proceed to balance another, and another, until all elements are balanced.
Balance chemical formulas by placing coefficients in front of them. Do not add subscripts, because this will change the formulas.
- Indicate the states of matter of the reactants and products.
Use (s) for solids.
Use (l) for liquids.
Use (aq) for species in solution in water.
Write the state of matter immediately following the formula of the substance it describes