Balancing Symbol Equations

In chemistry, equations show what is happening in a chemical reaction. The starting materials are known as the reactants (sometimes called reagents) and the new materials are called the products. Scientists use balanced symbol equations in order to describe chemical reactions. Calculations of reacting quantities can be made using these balanced equations so they are of great importance to anyone involved with chemistry. At first, balancing symbol equations can seem daunting but if you follow a few simple rules, it becomes a lot easier!

At high school, it is best to begin with a word equation so that you can quickly see that you have all of the reactants and products. Underneath that, write down the correct formula for each of the chemicals. This is the crucial step - if any of the formulae are wrong, the final equation may never balance. Once that is done, you can count the atoms of the individual elements on both sides of the reaction. Make two lists on a piece of rough paper, one for the atoms on the reagents side and another for the products. The Law of Conservation of Matter means that the products must contain exactly the same number and type of atoms as the reactants, but not joined together in the same way. When the two lists contain exactly the same numbers and types of atoms, the equation is balanced.

You can then start to balance the equation. Some equations will automatically be balanced but the majority won't be. You cannot change the formulae (unless you realize one of them is wrong), all you can do is to change the quantities of each formula. You do this by placing a number in front of the formulae as required e.g. 2NaCl or 3H₂O. This doubles, trebles, quadruples etc. ALL of the elements in the formula. NaCl means that you have one atom of sodium and one of chlorine. Placing a 2 in front doubles the numbers of both the sodium and chlorine atoms. This works with every formula. As you add a number, you need to update your lists of atoms.

Balancing symbol equations, which is only required on the higher tier paper, is much harder to describe than it is to do! Practice makes perfect so try your hand at this quiz and sharpen your equation balancing skills!