Lesson 12: Chemical Reaction Equations (Chemistry)

In this lesson, we will discuss the equations which are used to describe chemical reactions. These are a vital part of the study of chemistry because the equations illustrate how substances react and what the reaction produces. Don't worry thought, these equations are extremely easy to understand and only simple math is required to work with them at this point.

An example of a reaction equation would look like this: 2H2 + O2 --> 2H20.

This is a relatively simple equation which describes hydrogen burning in the presence of oxygen to form water. In the reaction equation, the --> can be thought of as saying "reacts to form". The components on the left of the --> are the ingredients of the reaction which are called the reactants. The reactants interact to form the components on the right of the --> which are called the products.

In reaction equations, there are two types of numbers involved, coefficients and subscripts. The coefficients, like the first 2 in both 2H2 and 2H2O, are used to balance the reaction equation so the number of atoms on the right side of the equation will equal the number of atoms on the left side of the equation. Think of the coefficients as saying 2 H2 molecules or 2 H2O molecules. This is necessary because we know matter can not be created or destroyed so an unbalanced equation does not accurately depict a legitimate chemical reaction.

Due to text limitations in blogger, think of the second 2 in 2H2 and 2H2O and the 2 in O2 as being subscripts or small numbers located near the bottom of the line. These represent multiple atoms bound to another atom. Think of the molecule H2O. There are two hydrogen atoms bound to the oxygen atom. Subscripts can be thought of as numbers which tell us how the molecules involved in the reactions are constructed as opposed to how many of those molecules are involved in the reaction.

Reaction equations are used to predict not only what products will be produced from a reaction, but how much of those products will be produced. In the following equation, Mg + 2Cl --> MgCl2, we know, if we put in 100 atoms of Mg and 200 atoms of Cl, we will receive 100 atoms of MgCl2. Chemists do not calculate exactly how many atoms are used and will be formed, but rather, the measurement of mols is used in conjunction with chemical reaction equations. We will cover this in later lessons.

More information on chemical reaction equations can be found at:

1. http://en.wikipedia.org/wiki/Chemical_equation
2. http://www.science.uwaterloo.ca/~cchieh/cact/c120/reaction.html

The second link is helpful but covers topics that we have not yet discussed so if you aren't sure what is going on, don't worry, we will cover it in later lessons.