Question

How to balance equations

Answer 1

Steps to balance a chemical equation.

1. Identify the reactants and the products in the reaction and write their chemical formulae.
2. Write the equation by putting the reactants on the left of the arrow and the products on the right.
3. Count the number of atoms of each element in the reactants and the number of atoms of each element in the products.
4. If the equation is not balanced, change the coefficients of the molecules until the number of atoms of each element on either side of the equation balance.
5. Check that the atoms are in fact balanced.

EXAMPLE

Balance the following equation:

Mg+HCl→MgCl2+H2

Identify the reactants and products
Write the equation for the reaction

Count the number of atoms of each element in the reactants and products
Reactants:
Mg=1 atom,
H=1 atom,
Cl=1 atom

Products:
​​​​​​Mg=1 atom,
H=2 atoms,
Cl=2 atoms

The equation is not balanced since there are two chlorine atoms in the product and only one in the reactants.
If we add a coefficient of 2 to the HCl to increase the number of H and Cl atoms in the reactants, the equation will look like this:

Mg+2HCl→MgCl2+H2

Check that the atoms are balanced
If we count the atoms on each side of the equation, we find the following:

Reactants:
Mg=1 atom,
H=2 atoms,
Cl=2 atoms

Products:
Mg=1 atom,
H=2 atoms,
Cl=2 atoms
The equation is balanced. The final equation is:

Mg+2HCl→MgCl2+H2