Question

Give two differences between double salt and complex salt.

Answer 1

Hint: An double salt is formed by the crystallisation in the ionic lattice of two different salts. Example of double salts include alum $({K_2}S{O_4}.A{l_2}{(S{O_4})_3}.24{H_2}O)$,potassium sodium tartrate etc. We can also define double salt as a mixture of two salts that gives two types of metal ions when dissolved in water. Doble salts can be analysed by determining the ions present in the aqueous solution.

Complete step by step solution: Complex salt contains complex neutral molecules, where a central metal atom ion or atom surrounded by a number of neutral atoms or ions. Examples of complex salts are potassium ferrocyanide $({K_4}[Fe{(CN)_6}])$, tetra amino cupric sulphate $(Cu(N{H_3})S{O_4})$ etc. Complex salts cannot be analysed by determination of the ions in the aqueous solution.
Two main difference between double salt and complex salt are given below :

| Double Salt | Complex Salt
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$1.$| Double Salts dissociates into simple ions when dissolved in water. Example- Mohr’s salt.| They do not dissociate into simple ions when dissolved in water. Example- Potassium ferrocyanide
$2.$| When two salts are crystallised together in stoichiometric ratio from their saturated solution to form double salts.| In complex salts it is made up of a central metal atom or ion which used to be surrounded by oppositely charged ions or neutral molecules.

Note: Hence we come to know about the differences between double salt and complex salts. One more difference is that in doble salt the metal atom or ion exhibits the normal valency whereas in complexes the negative ions or molecules surrounding the central metal atom are beyond its normal valency.