Question

Which of the following statement is true about potassium permanganate?

• A. It is isostructural with \( KClO_3 \)
• B. It is paramagnetic in nature
• C. It oxidizes oxalates to carbon monoxide
• D. The structure of permanganate ion is square planar
• E. It is prepared by fusion of \( MnO_2 \) with an alkali metal hydroxide and an oxidising agent

Hint:

Permanganate ion is tetrahedral, not square planar.

Answer 1

Answer: (E)

Step 1: Understanding the Properties of Potassium Permanganate (KMnO\(_4\)):
Potassium permanganate is a strong oxidizing agent with a distinctive deep purple color. Its properties are determined by the permanganate ion (MnO\(_4^-\)).
Step 2: Analyzing the Statements:
(A) It is isostructural with KClO\(_3\): "Isostructural" means having the same structure. The permanganate ion, MnO\(_4^-\), is tetrahedral. The chlorate ion, ClO\(_3^-\), is trigonal pyramidal. Therefore, KMnO\(_4\) and KClO\(_3\) are not isostructural. (Note: KMnO\(_4\) is isostructural with KClO\(_4\), as both MnO\(_4^-\) and ClO\(_4^-\) are tetrahedral). This statement is false.
(B) It is paramagnetic in nature: In MnO\(_4^-\), the oxidation state of Mn is +7. The electronic configuration of Mn is \([Ar] 3d^5 4s^2\). For Mn\(^{+7}\), the configuration is \([Ar] 3d^0\). Since there are no unpaired electrons, KMnO\(_4\) is diamagnetic. This statement is false.
(C) It oxidizes oxalates to carbon monoxide: In acidic medium, potassium permanganate oxidizes oxalate ions (C\(_2\)O\(_4^{2-}\)) to carbon dioxide (CO\(_2\)), not carbon monoxide (CO). The reaction is: \(2\text{MnO}_4^- + 5\text{C}_2\text{O}_4^{2-} + 16\text{H}^+ \rightarrow 2\text{Mn}^{2+} + 10\text{CO}_2 + 8\text{H}_2\text{O}\). This statement is false.
(D) The structure of permanganate ion is square planar: As mentioned in (A), the permanganate ion (MnO\(_4^-\)) has a tetrahedral structure, with the Mn atom at the center. This statement is false.
(E) It is prepared by fusion of MnO\(_2\) with an alkali metal hydroxide and an oxidising agent: This describes the commercial preparation of KMnO\(_4\). First, pyrolusite ore (MnO\(_2\)) is fused with an alkali like KOH in the presence of an oxidizing agent (like O\(_2\) or KNO\(_3\)) to form potassium manganate (K\(_2\)MnO\(_4\)). The green manganate is then electrolytically oxidized to permanganate. \(2\text{MnO}_2 + 4\text{KOH} + \text{O}_2 \rightarrow 2\text{K}_2\text{MnO}_4 + 2\text{H}_2\text{O}\). This statement is true.
Step 3: Final Answer:
The true statement about potassium permanganate is that it is prepared by the fusion of MnO\(_2\) with an alkali and an oxidizing agent.