Gujarat BoardEnglish MediumSTD 11 ScienceChemistryRedox Reactions5 Marks
Question
Which method can be used to find out strength of reductant/oxidant in a solution? Explain with an example.
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Answer
In redox systems, the titration method can be adopted to determine the strength of a reductant/ oxidant using a redox sensitive indicator. The usage of indicators in redox titration is illustrated below:
(i) In one situation, the reagent itself is intensely coloured, e.g.. permanganate ion, $\mathrm{MnO}_4^{-}$. Here, $\mathrm{MnO}_4^{-}$acts as the self indicator. The visible end point in this case is achieved after the last of the reductant $\left(\mathrm{Fe}^{2+}\right.$ or $\left.\mathrm{C}_2 \mathrm{O}_4^{2-}\right)$ is oxidised and the first lasting tinge of pink colour appears at $\mathrm{MnO}_4^{-}$ concentration as low as $10^{-5} \mathrm{~mol}\left(10^{-6} \mathrm{~mol} \mathrm{~L}^1\right)$. This ensures a minimal 'overshoot' in colour beyond the equivalence point, the point where the reductant and the oxidant are equal in terms of their mole stoichiometry.
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