General Principles of Isolation of Elements

Identify the incorrect pair from the following :

1. Fluoroapatite -3Ca3(PO4)2 CaF2
2. Carnallite -KCl MgCl2 6H2O
3. Cryolite -Na3AlF6
4. Fluorspar -BF3

Answer

(4) Fluorspar -BF3

Solution

Fluorspar (fluorite) is calcium fluoride, CaF2 — not BF3.

(A): Fluoroapatite = 3Ca3(PO4)2 CaF2 ⇒ (A) is correct

(B): Carnallite = KCl MgCl2 6H2O ⇒ (B) is correct

(C): Cryolite = Na3AlF6 ⇒ (C) is correct

(D): Fluorspar = CaF2 ⇒ (D) is the incorrect pair

∵ BF3 is a covalent gas; it does not occur as a mineral.

Answer: (4)