Which one of the following salts does not possess water of crystallization?

Water of crystallization refers to the fixed number of water molecules chemically combined in a salt's crystal structure [1]. Blue vitriol is copper(II) sulfate pentahydrate (CuSO4·5H2O), where five water molecules provide its characteristic blue color [1]. Washing soda is sodium carbonate decahydrate (Na2CO3·10H2O), containing ten water molecules. Mohr’s salt is a double salt, specifically ferrous ammonium sulfate hexahydrate (FeSO4(NH4)2SO4·6H2O), which contains six water molecules [2]. In contrast, Potassium permanganate (KMnO4) is an anhydrous salt. It exists as dark purple crystals that do not contain water of crystallization in their standard solid form [3]. While it dissolves readily in water to form a purple solution, the solid crystals themselves lack the chemically bound water molecules found in the other listed hydrated salts.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > Activity 2.15 > p. 32
2. [2] https://theses.gla.ac.uk/80629/1/27534988.pdf
3. [3] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 7: Particulate Nature of Matter > Think like a scientist > p. 110