Question

The ore that contains the metal in the form of fluoride is:
(A) magnetite
(B) sphalerite
(C) malachite
(D) cryolite

Answer 1

An attempt to this question can be made by identifying the ores. Upon that, write the chemical formula of each of these ores. If fluorine is part of the chemical formula and the oxidation state of fluorine in the compound is -1, then the metal is in the form of fluoride. This will help you arrive at the correct answer.

Complete step-by-step answer:
-Magnetite : It is a rock mineral and one of the chief ores for the extraction of iron. It is an oxide of iron and ferromagnetic in nature. The formula of the compound is : $F{{e}_{3}}{{O}_{4}}$.
-Sphalerite : It is a mineral and the main ore to obtain the metal zinc. It exists as the sulfide of zinc metal. The formula of the compound is : $ZnS$.
-Malachite : It is a rock obtained by weathering consisting of the metal copper. It is green in appearance. It exists as a carbonate of copper metal. The formula of the compound is : $C{{u}_{2}}C{{O}_{3}}{{(OH)}_{2}}$
-Cryolite : It is an uncommon mineral of the metal aluminum. It exists as a fluoride of aluminum and sodium metal. The formula of the compound is : $N{{a}_{3}}Al{{F}_{6}}$
Based on the above formulae of ores, we can conclude that the ore that contains the metal in the form of fluoride is cryolite.

Therefore, the correct answer is option (D).

Note: It is important to know that although cryolite is used to obtain aluminium, it is a very rare mineral. Due to its rarity it is possibly the only mineral found on Earth that is close to commercial extinction due to excessive mining. The chief ore of aluminium is bauxite and not cryolite.