The dark crystals of potassium permanganate are iso-structural with:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \(KClO_4\)
Isostructural crystals have the same crystal structure because their units have the same formula type and shape. Potassium permanganate forms dark purple (almost black) crystals that are isostructural with those of KClO4: both contain \( \ce{K^{+}} \) ions and tetrahedral XO4− ions (\( \ce{MnO4^{-}} \) and \( \ce{ClO4^{-}} \)) of nearly the same size.
NCERT (2026-27 edition):
Oxides and Oxoanions of Metals – “… Potassium permanganate forms dark purple (almost black) crystals which are isostructural with those of KClO4. The salt is not very soluble in water (6.4 g/100 g of water at 293 K), but when heated it decomposes at 513 K.”
\( \ce{2KMnO4 -> K2MnO4 + MnO2 + O2} \)