Redox Titration

Redox Titration

What is Redox Titration?

Redox titration is based on reduction and oxidation between the analyte and titrant. Titration is the most commonly applied method to determine the concentration or amount of a substance that is not known. The method is simple if the quantitative relationship between two reactants is known.

Oxidation refers to the process of addition of oxygen and reduction refers to the removal of oxygen or addition of hydrogen. Titration method is best suited to oxidation-reduction and acid-base reactions.

Redox Titration – Oxidation Reduction Titration

We conduct two separate redox titrations by using a standard permanganate solution. In the initial titration, you will find the percentage of hydrogen peroxide in a solution. In the second titration, you will find the percentage of iron in an iron salt. The titration method is adopted in redox systems to find the strength of an oxidant or reductant by using a sensitive indicator. The redox titrations that involve potassium permanganate are known as per manganometric titrations and MnO4– ions serve as the self-indicator.

The permanganate ion is a strong oxidizing agent mostly in acidic solution and used to analyze solutions that consist of different species, by titration. The deep colored MnO4– ion is reduced to make a colorless Mn2+ ion in these titration reactions.

Titration of KMnO4 against Oxalic acid

Prepare a standard Oxalic acid solution of about 250 ml.

The molecular mass of oxalic acid is calculated by,

H2C2O4.2H2O = 126

Since the weight of oxalic acid that is required to make 1000 ml of 1M solution is 126 g. Hence, the weight of oxalic acid needed to prepare 250 ml of 0.1 M solution is,

= 126/1000 x 250 x 0.1

= 3.15 g

To determine the strength of KMnO4 by the standard oxalic acid solution.

Oxalic acid is the analyte and KMnO4 is the titrant in this redox titration, while oxalic acid is the reducing agent and potassium permanganate is the oxidizing agent. The reaction between oxalic acid and potassium permanganate occurs in acidic medium, as permanganate ion is a powerful oxidizing agent in an acidic medium. The acidic nature is introduced by adding dilute H2SO4.

\(MnO_{4}^{-}\;+8H^{+}\;5e^{-}\rightarrow Mn^{2+}\;+4H_{2}O\)

KMnO4 acts as an indicator of where the permanganate ions are deep purple color. MnO4– is reduced to colorless manganous ions (Mn2+) in the acidic medium. The last drop of permanganate gives a light pink color on reaching the endpoint. The following chemical equation can represent the reaction that occurs.

Molecular equation

\(2Kmno_{4}\;+3H_{2}SO_{4}\rightarrow K_{2}SO_{4}\;+2MnSO_{4}\;+3H_{2}O\;+5[O]\)

\(H_{2}C_{2}O_{4}.2H_{2}O\;+[O]\rightarrow 2CO_{2}\;+3[H_{2}O]\times 5\)

Complete Reaction

\(2KMnO_{4}\;+3H_{2}SO_{4}\;+5H_{2}C_{2}O_{4}.2H_{2}O\rightarrow K_{2}SO_{4}\;+2MnSO_{4}\;+18H_{2}O\;+10CO_{2}\)

Ionic equation

\(MnO_{4}^{-}\;+8H^{+}\;+5e^{-}\rightarrow Mn^{2+}\;+4H_{2}O]\times 2\)

\(C_{2}O_{4}^{2-}\rightarrow 2CO_{2}\;+2e^{-}]\times 5\)

Complete Reaction

\(2MnO_{4}^{-}\;+16H^{+}\;+5C_{2}O_{4}^{2-}\rightarrow 2Mn^{2+}\;+8H_{2}O\;+10CO_{2}\)

From the above-balanced chemical reaction, it gets clear that 2 moles of KMnO4 react with 5 moles of oxalic acid.

To know more about acid-base redox titrations along with potentiometric titrations, download BYJU’S – the learning app

Practise This Question

Boron form covalent compound due to