Consider the reactions
a) `6CO_(2)(g)+6H_(2)O(I)toC_(6)H_(12)O_(6)(aq)+6O_(2)(g)`
b) `O_(3)(g)+H_(2)O_(2)(I)toH_(2)O(I)+2O_(2)(g)`
Why it is more appropriate to write these reaction as
a) `6CO_(2)(g)+12H_(2)O(I)toC_(6)H_(12)O_(6)+6H_(2)O(I)+6O_(2)(g)`
b) `O_(3)(g)+H_(2)O_(2)(I)toH_(2)O(I)+O_(2)(g)+O_(2)(g)`
Also suggest a technique to investigate the path of the above (a) and (b) redox reactions.

Explanation

Plants absorb carbon dioxide from air, water from soil and convert them into carbohydrates in the presence of sunlight and Chlorophyll. This process is known as photosynthesis.
During photosynthesis plants liberate oxygen. The oxygen will be liberated from water but not from carbon dioxide. The following reaction cannot explain the liberation of oxygen from water because in this reaction from `6H_(2)O` molecules only `3O_(2)` can be liberated.
`6CO_(2)(g)+6H_(2)O(l)toC_(6)H_(12)O_(6)(aq)+6O_(2)(g)`
But the following reaction can explain the liberation `6O_(2)` molecules from water.
`6CO_(2)(g)+12H_(2)O(l)toC_(6)H_(12)O_(6)(aq)+6H_(2)O(l)+6CO_(2)(g)`
The path of the reaction can be traced by taking labile `""^(18)O` in `H_(2)O`. The liberated oxygen contain the total labile `""^(18)O` which indicates the oxygen is liberated from water.
`6CO_(2)(g)+12H_(2)""^(18)O(l)toC_(6)H_(12)O_(6)(aq)+6H_(2)O(l)+6""^(18)O_(2)(g)`
b) The reaction between `O_(3)andH_(2)O_(2)` can be written as follows :

So it is appropriate to the equation as above instead of
`O_(3)+H_(2)O_(2)toH_(2)O+2O_(2)`
In the reaction `O_(3)+H_(2)O_(2)toH_(2)O+O_(2)+O_(2)`
One of the `O_(2)` liberated from `O_(3)` and the another from `H_(2)O_(2)`. This can be traced by using `""^(18)O` isotope in `H_(2)O_(2)`.