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How to Write Chemical Equations in Chemistry

The word "chemistry" comes from a word that means "change." Chemical compounds frequently change into something else. Chemical equations are a way of expressing this change. A typical chemical equation will have a few compounds added together followed by a right pointing arrow and then some other compounds. The equation is supposed to suggest that the compounds to the left of the arrow combine to produce the compounds to the right of the arrow.

Instructions

- 1
  Start writing a chemical equation by identifying the reactants -- the things that react -- and the products -- the things that are produced. For example, natural gas burns in the presence of oxygen to produce carbon dioxide and water vapor. This reaction also produces heat, but that is not part of the chemical equation. In words, this is natural gas + oxygen --> carbon dioxide + water vapor. In chemical symbols it would be CH4 + O2 --> CO2 + H2O. The oxygen is written O2 because atoms of oxygen always bind to each other in pairs, so all oxygen supplies are molecules of O2.
- 2
  Balance the equation. CH4 + O2 --> CO2 + H2O is inaccurate because there are not the same number of the same atoms on each side of the arrow. The carbon atoms balance, but there are more hydrogen atoms on the left and more oxygen atoms to the right of the arrow. We can put in a couple of coefficients that will make the same amount of each type of atoms to the left and right of the arrow. This will make the description of the reaction more exact, because atoms are not created or lost in the reaction. The formula CH4 + 2O2 --> CO2 + 2H2O has the same number of atoms of each element, so it more accurately describes the reaction. One molecule of methane combines with two molecules of oxygen to produce one molecule of carbon dioxide and two molecules of water.
- 3
  Use extra symbols to describe the reactions more accurately. The state of the molecules -- solid, liquid or gas -- can be indicated by letters in parentheses after the molecules. An upward pointing arrow is sometimes used to indicate that a gas forms and a downward pointing arrow is used to indicate a solid forms and falls to the bottom of a solution.

Nature