Question

Potassium permanganate on heating at 513 K gives a product which is :

• A. paramagnetic and colourless
• B. diamagnetic and colourless
• C. paramagnetic and green
• D. diamagnetic and green

Hint:

To determine if a transition metal compound is paramagnetic or diamagnetic, always find the oxidation state of the metal, write down its d-electron configuration, and check for unpaired electrons. Any unpaired electrons will result in paramagnetism.

Answer 1

The Correct Option is C

Potassium permanganate (\( KMnO_4 \)) is known for undergoing thermal decomposition when heated. The reaction for its decomposition is:

2KMnO_4 \xrightarrow{513 \, K} K_2MnO_4 + MnO_2 + O_2

This reaction produces the solid green compound potassium manganate (\( K_2MnO_4 \)), manganese dioxide (\( MnO_2 \)), and oxygen gas (\( O_2 \)).

Let's analyze the properties of the product \( K_2MnO_4 \):

1. Paramagnetism: The compound \( K_2MnO_4 \) contains the \( Mn^{6+} \) ion. Manganese in the +6 oxidation state has unpaired electrons, hence it exhibits paramagnetic behavior.
2. Color: Manganese compounds can vary in color based on their oxidation states. \( K_2MnO_4 \) is known to have a green color due to its electronic transitions.

Therefore, the product formed upon heating potassium permanganate at 513 K is both paramagnetic and green.

Based on these observations, the correct answer is: paramagnetic and green.