Balancing Symbols
Chemistry: Edexcel IGCSE, topic 5.1.2
Balancing Chemical Equations
Chemical equations must be balanced to make sure that there are the same number of atoms of each element before and after a reaction. The reaction of hydrogen with oxygen to make water will be used as an example of how to do this:
Unbalanced equation
- The unbalanced symbol equation for this reaction is:
- H2 + O2 → H2O
- The equation is unbalanced because there are 2 atoms of oxygen on the left hand side of the equation, but only 1 on the right hand side.
Still unbalanced equation
- We can increase the number of oxygen atoms on the right hand side by adding an H2O molecule:
- H2 + O2 → 2H2O
- However, the equation is still unbalanced as there are now more hydrogen atoms on the right hand side than on the left hand side.
Balanced equation
- The final step is to add an H2 molecule to the left hand side:
- 2H2 + O2 → 2H2O
- Our equation is now balanced.
Test yourself on Balancing Symbols
H2 + O2 → 2H2O
Why is this equation unbalanced?Select the true statement in each pair.
In the process of balancing chemical equations, why is it important to have the same number of atoms of each element on both sides of the equation?
Which step in balancing the chemical equation for the reaction of hydrogen with oxygen to make water ensures that there are the same number of oxygen atoms on both sides of the equation?
What is the balanced symbol equation for the reaction of hydrogen with oxygen to make water?