Question

Consider the reactions: 

(a) 6CO_2(g) + 6H₂O_(l) → C₆H₁₂O_6(aq) + 6O_2(g) 

(b) O_3(g) + H₂O_2(l) → H₂O_(l) + 2O_2(g) 

Why it is more appropriate to write these reactions as: 

(a) 6CO_2(g) + 12H₂O_(l) → C6 H₁₂ O_6(aq) + 6H₂O_(l) + 6O_2(g) 

(b) O_3(g) + H2O_{2 (l)} → H2O_(l) + O_2(g) + O_2(g) 

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

Answer 1

(a)The process of photosynthesis involves two steps. 

Step 1: 

H₂O decomposes to give H₂ and O₂. 

Step 2: 

The H₂ produced in step 1 reduces CO₂, thereby producing glucose (C₆H₁₂O₆) and H₂O. 

Now, the net reaction of the process is given as: 

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 H₂O₂. 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. 

The path of this reaction can be investigated by using . H₂O₂¹⁸ or O₃¹⁸