question_answer 19)

Justify that following reactions are redox reactions: (a) \[CuO(s)+{{H}_{2}}(g)\to Cu(s)+{{H}_{2}}O(g)\] (b) \[F{{e}_{2}}{{O}_{3}}(s)+3CO(g)\to 2Fe(s)+3C{{O}_{2}}(g)\] (c) \[4BC{{l}_{3}}(g)+3LiAl{{H}_{4}}(s)\to 2{{B}_{2}}{{H}_{6}}(g)+LiCl(s)+3AlC{{l}_{3}}(s)\](d) \[2K(s)+{{F}_{2}}(g)\to 2{{K}^{+}}{{F}^{-}}(s)\] (e) \[4N{{H}_{3}}(g)+5{{O}_{2}}(g)\to 4NO(g)+6{{H}_{2}}O(g)\]  

Answer:

(a) In photosynthesis, \[{{O}_{2}}\] is released from water, not from carbon dioxide. It was confirmed by radioactive tracer technique. The mechanism may be given as: \[6C{{O}_{2}}(g)+6{{H}_{2}}{{O}^{*}}6{{H}_{2}}O\to {{C}_{6}}{{H}_{12}}{{O}_{6}}(aq)\] \[+6{{H}_{2}}O(l)+6O_{2}^{*}\] (b) Mechanism of this reaction may be given as, \[\begin{align} & {{O}_{3}}(g)\to {{O}_{2}}(g)+O(g) \\ & {{H}_{2}}{{O}_{2}}+O(g){{H}_{2}}O(l)+{{O}_{2}}(g) \\ & \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ \\ & \frac{{{H}_{2}}{{O}_{2}}(l)+{{O}_{3}}(g)\to {{H}_{2}}O(l)+{{O}_{2}}(g)+{{O}_{2}}(g)}{{}} \\ \end{align}\]