8.9 Consider the reactions:

(a) 6 CO2(g) + 6H2O(l) C6 H12 O6(aq) + 6O2(g)

(b) O3(g) + H2O2(l) H2O(l) + 2O2(g)

Why it is more appropriate to write these reactions as :

(a) 6CO2(g) + 12H2O(l) C6 H12 O6(aq) + 6H2O(l) + 6O2(g)

(b) O3(g) + H2O2 (l) H2O(l) + O2(g) + O2(g)

Also suggest a technique to investigate the path of the above (a) and (b) redox reactions.

(a)The process of photosynthesis involves two steps. Step 1: H2O decomposes to give H2 and O2.2H2Ol2H2g+O2g  Step 2:The H2 produced in step 1 reduces CO2, thereby producing glucose (C6H12O6) and H2O. 6CO2g+12H2gC6H12O6g+6H2OlNow, the net reaction of the process is given as:2H2Ol2H2g+O2g]×66CO2g+12H2gC6H12O6g+6H2Ol6CO2g+12H2OlC6H12O6g+6H2Ol+602g

It is more appropriate to write the reaction as given above because water molecules are
also produced in the process of photosynthesis. The path of this reaction can be investigated by using radioactive H2O18 in place of H2O.

(b) O2 is produced from each of the two reactants O3 and H2O18. For this reason, O2 is written twice.
The given reaction involves two steps. First, O3 decomposes to form O2 and O. In the second step, H2O2 reacts with the O produced in the first step, thereby producing H2O and O2.
O3gO2g+OgH2O2l+OgH2Ol+O2gH2O2l+O3gH2Ol+O2g+O2gThe path of this reaction can be investigated by using H2O218or O318.