Question

The dark purple colour of \(KMnO_4\) disappears in the titration with oxalic acid in acidic medium. The overall change in the oxidation number of manganese in the reaction is :

• A. 5
• B. 1
• C. 7
• D. 2

Answer 1

The Correct Option is A

To determine the overall change in the oxidation number of manganese in the reaction between potassium permanganate (\(KMnO_4\)) and oxalic acid in acidic medium, we need to analyze the redox reaction that occurs.

In this redox reaction, potassium permanganate (\(KMnO_4\)) acts as an oxidizing agent. The manganese in \(KMnO_4\) has an oxidation state of +7. During the reaction, the manganese is reduced, and its oxidation state changes.

The reaction in acidic medium can be represented as follows:

2 KMnO_4 + 5 H_2C_2O_4 + 6 H^+ \rightarrow 2 Mn^{2+} + 10 CO_2 + 8 H_2O + 2 K^+

In this reaction, the manganese (\(Mn\)) in \(KMnO_4\) is reduced from an oxidation state of +7 to an oxidation state of +2 in \(Mn^{2+}\).

The change in oxidation state for manganese is calculated as follows:

• Initial oxidation state of Mn in \(KMnO_4\): +7
• Final oxidation state of Mn in \(Mn^{2+}\): +2
• Change in oxidation number: 7 - 2 = 5

Thus, the overall change in the oxidation number of manganese in the reaction is 5.

The correct answer is, therefore, 5.

This process illustrates a typical redox reaction in acidic medium where \(KMnO_4\) is a common laboratory reagent, often used due to its strong oxidizing properties.