Q.Give the difference between double salts and coordination compounds.

Step 1. Both double salts and coordination compounds are formed by mixing two or more stable compounds in solution and allowing them to crystallise (Section 5.1) -- on paper, both can look like a simple combination of formulas.

Step 2. The defining difference shows up in solution: a double salt, such as Mohr's salt FeSO₄.(NH₄)₂SO₄.6H₂O, loses its identity completely and dissociates into ALL of its simple constituent ions -- a qualitative test on Mohr's salt answers positive for Fe²⁺, NH₄⁺ and SO₄²⁻, exactly as if the two parent salts (ferrous sulphate and ammonium sulphate) had simply been mixed.

Step 3. A coordination compound, such as potassium ferrithiocyanate K₃[Fe(SCN)₆], instead has a complex ion, [Fe(SCN)₆]³⁻, that retains its identity in solution and does NOT dissociate into its simple constituent ions -- a qualitative test on this compound does not answer positive for free Fe³⁺ or free SCN⁻. …

State the defining behavioural difference -- full dissociation into simple ions (double salt) versus retained complex-ion identity (coordination compo …

• Trying to distinguish the two purely by formula appearance rather than by their actual behaviour/dissociation in solution, which is the real, testable distinction. …