Question

In the following reaction:
\[3C{{l}_{2}}+6NaOH\to NaCl{{O}_{3}}\,+5NaCl\,+\,3{{H}_{2}}O\]
The element which loses as well as gains electrons is:
a) Na
b) O
c) Cl
d) None of these

Answer 1

Hint: The reaction given here is a special type of redox reaction called disproportionation reaction, where oxidation (loss of electron) and reduction (gain of an electron) of an element occurs simultaneously

Complete answer:\[3C{{l}_{2}}+6NaOH\to NaCl{{O}_{3}}\,+5NaCl\,+\,3{{H}_{2}}O\]
In the case of \[NaCl{{O}_{3}}\], the Chlorine gas is reduced \[Cl{{O}_{3}}^{-}\]ion.
The oxidation state of O in \[NaCl{{O}_{3}}\] is -2 and the oxidation state of Na in \[NaCl{{O}_{3}}\] is +1.

The equation to find the oxidation state of is:
\[1(Oxidation\,state\,of\,Na)\,+\,1(Oxidation\,state\,of\,Cl)\,+\,3(Oxidation\,state\,of\,O)\,=\,0\]

On rearranging the above equation for the oxidation state of Cl.
\[\,1(Oxidation\,state\,of\,Cl)=\,-[1(Oxidation\,state\,of\,Na)\,+3(Oxidation\,state\,of\,O)]\]

Finally, we will substitute the oxidation state of O i.e. +1 and the oxidation state of Na i.e. +1 in the equation.
\[\begin{align}
  & \,Oxidation\,state\,of\,Cl=\,-[1(+1)\,+3(-2)] \\
 & \,\,\,\,\,\,\,\,\,\,\,\,\,\,=-(1-6) \\
 & \,\,\,\,\,\,\,\,\,\,\,\,\,\,=-(-5) \\
 & \,\,\,\,\,\,\,\,\,\,\,\,\,\,=+5 \\
\end{align}\]
Similarly, in the case of NaCl, we can see that Chlorine gas is reduced to \[C{{l}^{-}}\]ion. The oxidation of Na in NaCl is +1 and the oxidation state of Cl is -1.

We can see that on reaction with NaOH, Cl goes from an oxidation 0 in the chlorine molecules on the left-hand side to -1 oxidation state in the NaCl and +5 oxidation state in the \[NaCl{{O}_{3}}\]. Therefore, it is getting both oxidized (loss of electrons) and reduced (gain of electrons) at the same time.

Hence, the correct option is (c).

Note: The NaOH used here is in hot and aqueous form, the same reaction will give different products when temperature and concentrations are changed. Cold dilute sodium hydroxide will give sodium chloride, sodium chlorate(i) and water as products.