How is the chemical reaction for photosynthesis balanced

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gsenviro eNotes educator| Certified Educator

In the process of photosynthesis, plants (containing chlorophyll) use carbon dioxide, water and light energy and produce chemical energy (in the form of sugars) and oxygen. The balanced chemical reaction is given as:

`6CO_2 + 6H_2O + (light) -> C_6H_(12)O_6 + 6O_2`

This reaction is significant for a number of reasons. Photosynthesis provides us food (in the form of sugars and plat parts). It maintains the oxygen levels in our atmosphere (lack of which will kill aerobic life forms life us) and get rid of excess carbon dioxide (excess of which may lead to global warming and climate change). 

Interestingly, we (human beings) and other higher life forms (including animals) use an opposite chemical reaction for our survival: we consume food and oxygen, and produce carbon dioxide and water (no light energy). 

Hope this helps.

yaz711 | Student

During photosynthesis the reaction taking place follows the conservation of matter i.e. the amount of matter present before and after a chemical equation must be the same. Therefore the number of X atoms present in the reactants side (left) much be equal to the number of X atoms present in the products (right).

For this particular equation it is best to start by taking note of the number of carbon atoms present in glucose since these small subscripts indicate the amount of carbon present in a molecule of glucose. In this case the amount of Carbon Dioxide required to produce the 6 Carbon atoms present in glucose are six Carbon Dioxide molecules, hence the 6 indicated to the left.

This method can be carried out for both Hydrogen and Oxygen. In Order to compensate 12 atoms of Hydrogen in glucose 6 molecules of water are required are required to react. Since water contains 2 atoms of Hydrogen only six more molecules are needed for the reaction to take place. 6 x 2 Hydrogen = 12 H atoms. Lastly the Oxygen (O) atoms can be balanced in a manner such as:
6*(2 O atoms) + 6*(1 O atoms) = 1*(6 O atoms) + x*(2 O atoms)

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