Q

# Consider the reaction 6CO2(g) + 6H2O(l) ----C6H12O6(aq)+ 6O2(g)

8.9 Consider the reactions:
$(a) 6CO_{2}_{(g)}+6H_{2}O_{(l)}\rightarrow C_{6}H_{12}O_{6}_{(aq)}+6CO_{2}_{(g)}$

$(b) O_{3}_{(g)}+H_{2}O_{2}_{(l)}\rightarrow H_{2}O(l) +2O_{2}(g)$
Why it is more appropriate to write these reactions as :

$(a) 6CO_{2}_{(g)}+12H_{2}O_{(l)}\rightarrow C_{6}H_{12}O_{6}_{(aq)}+6H_{2}O_{(l)}+6CO_{2}_{(g)}$

$(b) O_{3}_{(g)}+H_{2}O_{2}_{(l)}\rightarrow H_{2}O(l) +O_{2}(g)+O_{2}_{(g)}$

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

Views

(a) In the photosynthesis process-

step 1- the    liberation of  $O_{2}$ and  $H_{2}$  -->        $2H_{2}O\rightarrow O_{2}+2H_{2}$

step-2 The $H_{2}$ produced in above reduces the $CO_{2}$ into glucose$(C_{6}H_{12}O_{6})$ and water$(H_{2}O)$

$6CO_{2}+12H_{2}\rightarrow C_{6}H_{12}O_{6}+6H_{2}O$

So, the final net reaction is

$2H_{2}O\rightarrow CO_{2}+2H_{2}]*6\\+6CO_{2}+12H_{2}\rightarrow C_{6}H_{12}O_{6}+6H_{2}O\\------------------\\6CO_{2}+12H_{2}O\rightarrow C_{6}H_{12}O_{6}+6H_{2}O$

It is more appropriate to write the reaction as above because water$(H_{2}O)$ molecule also produced in photosynthesis reaction.

The path of reaction can be investigated by using the radioactive $H_{2}O^{18}$ instead of  $(H_{2}O)$

(b)

$\\O_{3}(g)\rightarrow O_{2}(g)+O(g)\\ H_{2}O_{2}(l)+O(g)\rightarrow H_{2}O(l)+O_{2}(g)\\ ---------------\\ H_{2}O_{2}(l)+O_{3}(g)\rightarrow H_{2}O(l)+O_{2}(g)+O_{2}(g)$ (the final net reaction)

Dioxygen is produced from both steps, one from the decomposition of ozone ($O_{3}$) and other is from the reaction of hydrogen peroxide with(O)

• The path of the reaction can be investigated by using $O^{18}_{3}/ H_{2}O^{18}$.

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