Question

Which method can be used to find out the strength of reductant/oxidant in a solution? Explain with an example.

Answer 1

Strength of a reductant (reducing agent) or oxidant (oxidizing agent) can be found out by measuring the relative electrode potential when it's connected in a solution using a cell.

Elements under consideration can be made electrode of a standard cell whose electrode potential is already known.

For example, If $F{e}^{3+}/Fe$ is the electrode we want to test with Standard Hydrogen electrode(SHE), then half cell reactions are given below

$H^{+}+e^{-}\to \frac{1}{2}{H}_2$

$E^{\ominus }=0.0$

$F{e}^{3+}+e^{-}\to F{e}^{2+}$
$E^{\ominus }=0.0$
$E_{cell}^{\ominus }=E_{cathods}^{\ominus }-E_{anode}^{\ominus }$

$E_{cell}^{\ominus }=0.77-0$
$E_{cell}^{\ominus }=0.77V$

Here , $E_{cell}^{\ominus }>0$ so the reaction is feasible i.e, reduction of $F{e}^{3+}$ is spontaneous, Hence, we can conclude that tendency of $F{e}^{3+}$
ion to undergo reduction is more as compared to hydrogen.