The entities which do not dissociate into simple ions are:
(A) \([Fe(CN)_6]^{4-}\)
(B) \(KCl.MgCl_2. 6H_2O\)
(C) \(K_4[Fe(CN)_6]\)
(D) \(KAl(SO_4)_2. 12H_2O\)
(E) \(FeSO_4.(NH_4)_2SO_4.6H_2O\)
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A) and (C) only
A complex ion keeps its identity in solution: the metal–ligand bonds are not broken. A double salt exists only in the solid; in water it dissociates completely into simple ions, and the solution gives the tests of every ion present.
(A) [Fe(CN)6]4− — a complex ion; it does not break up into \( \ce{Fe^{2+}} \) and \( \ce{CN^{-}} \).
(B) KCl·MgCl2·6H2O (carnallite) — a double salt: \( \ce{K^{+}} \) + \( \ce{Mg^{2+}} \) + \( \ce{3Cl^{-}} \).
(C) K4[Fe(CN)6] — a coordination compound; it ionises only as \( \ce{4K^{+}} \) + \( \ce{[Fe(CN)6]^{4-}} \), and the complex ion stays intact.
(D) KAl(SO4)2·12H2O (potash alum) — a double salt: \( \ce{K^{+}} \) + \( \ce{Al^{3+}} \) + \( \ce{2SO4^{2-}} \).
(E) FeSO4·(NH4)2SO4·6H2O (Mohr’s salt) — a double salt: \( \ce{Fe^{2+}} \) + \( \ce{2NH4^{+}} \) + \( \ce{2SO4^{2-}} \).
NCERT (2026-27 edition):
Difference between a Double Salt and a Complex
