2.6.4

Balancing Chemical Equations

Test yourself

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:

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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.
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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.
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Balanced equation

  • The final step is to add an H2 molecule to the left hand side:
    • 2H2 + O2 → 2H2O
  • Our equation is now balanced.

Jump to other topics

1Biology

1.1Cells, Tissues & Organs

1.2Reproduction & Variation

1.3Ecological Relationships & Classification

1.4Digestion & Nutrition

1.5Plants & Photosynthesis

1.6Biological Systems & Processes

2Chemistry

2.1Particles

2.2Chemical Reactions

2.3Atoms, Elements, Compounds

2.4The Periodic Table

2.5Materials & the Earth

2.6Reactivity

2.7Energetics

2.8Properties of Materials

3Physics

3.1Energy

3.2Forces & Motion

3.3Waves

3.4Electricity & Magnetism

3.5Matter

3.6Space Physics

4Thinking Scientifically

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