JEE Chemistry 2023 Question with Solution

Given: Four compounds are listed and we need to identify which are double salts.

Find: Which among (A), (B), (C) and (D) are examples of double salts.

A double salt dissociates completely into its constituent ions in water, whereas a coordination compound does not dissociate fully because complex ions remain intact.

• (A) $FeSO_4.(NH_4)_2SO_4.6H_2O$ is Mohr's salt, a double salt.
• (B) $CuSO_4.4NH_3.H_2O$ is a coordination compound, not a double salt.
• (C) $K_2SO_4.Al_2(SO_4)_3.24H_2O$ is potash alum, a double salt.
• (D) $Fe(CN)_2.4KCN$ is a coordination compound, not a double salt.

Therefore, the correct examples of double salts are (A) and (C). Hence the correct option is A.

Given: The compounds are to be classified as either double salts or coordination compounds.

Find: The correct combination among the listed answer choices.

Principle used: Double salts retain identity only in crystalline state and dissociate completely in aqueous solution into simple ions. Coordination compounds form complex ions and therefore do not dissociate completely into all constituent species.

From the analysis:

1. (A) $FeSO_4.(NH_4)_2SO_4.6H_2O$ — Mohr's salt — double salt.
2. (B) $CuSO_4.4NH_3.H_2O$ — coordination compound.
3. (C) $K_2SO_4.Al_2(SO_4)_3.24H_2O$ — potash alum — double salt.
4. (D) $Fe(CN)_2.4KCN$ — ferrocyanide-type complex — coordination compound.

So the correct set is A and C only.

The solution states Option C, but that conflicts with the explained conclusion and the listed options. Since A and C only corresponds to the first listed option, the defensible answer is option A.