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

Solution

Chemistry ma’am · 3 steps

Heat KMnO₄ and you get green manganate: Mn drops from +7 to +6 and gains one unpaired d electron.

1. The reaction. At 513 K, potassium permanganate decomposes into potassium manganate, manganese dioxide and oxygen. The product this question means is K₂MnO₄.

   2KMnO₄ →(513 K) K₂MnO₄ + MnO₂ + O₂

   Ion	Oxidation state of Mn	d configuration	Unpaired electrons	Magnetic nature and colour
   MnO₄⁻ (permanganate)	+7	3d⁰	0	diamagnetic, purple
   MnO₄²⁻ (manganate)	+6	3d¹	1	paramagnetic, green

2. Why green. Both ions get their colour from charge transfer, from oxygen to manganese, and not from d–d transitions. Manganate absorbs at a different wavelength, so it looks dark green instead of purple.
3. So. K₂MnO₄ has one unpaired electron on Mn⁶⁺, so it is paramagnetic, and it is green. That is option (d).

The idea to keep. For magnetism, count the d electrons from the oxidation state: d⁰ is diamagnetic, anything with an unpaired electron is paramagnetic. For colour, remember permanganate is purple and manganate is green.

Answer from the NTA final answer key. Solution by PrepWiser.