Question

Identify tthe compounds which are reduced and oxidised in the following reaction.
$3N_2{H}_4+2Br{O}_3^{-}\to 3N_2+2B{r}^{-}+6H_{2}O$

• A. $N_2{H}_4$ is oxidised and $Br{O}_3^{-}$is reduced .
• B. $Br{O}_3^{-}$ is oxidised and $N_2{H}_4$ is reduced.
• C. $Br{O}_3^{-}$ is both reduced and oxidised.
• D. This is not a redox reaction.

Answer 1

The correct option is A $N_2{H}_4$ is oxidised and $Br{O}_3^{-}$is reduced .

Separating the oxidation and reduction reaction from the redox reaction:

$3N_2{H}_4+2Br{O}_3^{-}\to 3N_2+2B{r}^{-}+6H_{2}O$

assigning the oxidation number on central atom ($N$ and $Br$) in each molecules by considering oxidation number of $H=+1,O=-2$ we get oxidation state as:

$3{\stackrel{-2}{N}}_2{H}_4+2[\stackrel{+5}{Br}{O}_3{]}^{-}\to 3\stackrel{0}{N_2}+2\stackrel{-1}{B{r}^{-}}+6H_{2}O$

as the oxidation number of $N$ changes from -2 to 0 as:

$N_2{H}_4\to N_2$

its a oxidation reaction where $N_2{H}_4$ gets oxidized

Similarly, as the oxidation number of $Br$ changes from +5 to -1 as:

$Br{O}_3^{-}\to B{r}^{-}$

its a reduction reaction where $Br{O}_3^{-}$ gets reduced