Chemical reactions can be written as an equation with molecules on each side of the equation. Balancing equations is about ensuring that the number of atoms of each element on the left hand side of an equation is equal to the number of atoms of each element on the right hand side of the equation. For instance, aerobic respiration can be written as:Glucose + Oxygen ---> Carbon Dioxide and Water [+Energy] (as an aside, respiration is the combustion of glucose)Glucose can be written with the chemical formula: C₆H₁₂O₆This means that each molecule of glucose contains 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms.We can write the whole respiration equation using chemical formulas:C₆H₁₂O₆ + O₂---> CO₂+H₂OEach glucose molecule contains 6 carbon atoms, but each carbon dioxide molecule only contains 1 carbon atom. Balancing equations means to ensure there are the same number of each atoms on each side of the equation. In this case, for each glucose molecule we require 6 carbon dioxide molecules. We can now look to balance the hydrogen atoms. On the left hand side, the glucose molecule contains 12 hydrogen atoms. On the left hand side, the water molecule contains 2 hydrogen atoms. Hence, for each glucose molecule we need 6 water molecules. C₆H₁₂O₆ + O₂---> 6 CO₂+6 H₂OWe can now check that the oxygen atoms. On the left hand side, we have 6 oxygen atoms in the glucose molecule and 2 oxygen atoms in the oxygen molecule making a total of 8. On the right, we have 12 oxygen atoms in the 6 carbon dioxide molecules (6*2=12) and 6 oxygen atoms in the 6 water molecules making a total of 18. We therefore require 10 additional oxygen atoms on the left hand side, which are provided by 5 additional oxygen molecules.Thus, are final balanced equation is:C₆H₁₂O₆ + 6 O₂---> 6 CO₂+6 H₂OThe following are all examples of balanced equations:C + O₂ ---> CO₂2H₂ +O₂ ---> 2H₂O6H₂O + 6CO_{2 --->}C₆H₁₂O₆ + 6O₂ [this last equation represents photosynthesis]

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