Question

Fluorine reacts with ice and results in the change: $H_{2}O(s)+F_{2}(g) \longrightarrow HF(g)+HOF(g)$, Justify that this reaction is a redox reaction.

Answer 1

The chemical reaction which involves oxidation and reduction reactions are called redox reaction.

Fluorine reacts with ice to form hydrogen fluoride and HOF.

The given chemical reaction is as follows.

${ H }_{ 2 }O\quad \quad +\quad { F }_{ 2 }\quad \rightarrow \quad HF\quad +\quad HOF$

Let's give the oxidation numbers to the reactants as well as products.

$\begin{matrix} +1 \\ { H }_{ 2 } \end{matrix}\begin{matrix} -2 \\ O \end{matrix}\quad +\quad \begin{matrix} 0 \\ { F }_{ 2 } \end{matrix}\quad \rightarrow \quad \begin{matrix} +1 \\ H \end{matrix}\begin{matrix} -1 \\ F \end{matrix}\quad +\quad \begin{matrix} +1 \\ H \end{matrix}\begin{matrix} -2 \\ O \end{matrix}\begin{matrix} +1 \\ F \end{matrix}$

From the above reaction, we observe that the oxidation number of F increases from 0 in ${ F }_{ 2 }$ to + 1 in HOF and also oxidation number drops from 0 in ${ F }_{ 2 }$ to -1 in HF.  

Therefore, F is oxidized and reduced in the above reaction. Therefore, this reaction is referred as redox reaction.