Test: Minerals and ores - JEE MCQ

Ellingham diagrams are based on thermodynamic concepts. It does not tell anything about the kinetics of the reduction process.

The ore is crushed into a fine powder and mixed with water to form suspension.

Lime stone (CaCO₃) used in the extraction of Fe from haematite in blast furnace get decomposed to CaO, which removes silicate impurity (gangue) of the ore as molten slag.

At cathode
At anode

In the extraction of silver from cyanide process (also Mac-Arthur Forrest process), the siliver compound dissolve in NaCN solution forming a
soluble complex salt, in presence of air, then silver is precipitated from this complex salt by the addition of Zn, because Zn being more reactive displaces the Ag.

is cryolite and used in the electrolysis of alumina to lower the melting point and increase electrical conductivity.

In blast furnace at about , calcium carbonate is almost completely decomposed to give which acts as a flux and combines with present as impurity (gangue) in the ore to form calcium silicate (fusible slag)

CaO(s) + SiO₂(s) ⟶ CaSiO₃( s)
(basic flux) (acidic flux) 

Fused alumina is a bad conductor of electricity. Therefore, cryolite and fluorspar are added to purified alumina which not onlymake alumina a good conductor of electricity but also reduce the melting point of the mixture to around .

Roasted mass obtained from roasting step is called matte.

During extraction of iron from haematite ore, roasted ore, along with coke and limestone is heated in blast furnance. Here coke behaves as reducing agent and limestone is worked as flux. In this process, in reducing zone , spongy iron is obtained. In slag zone , limestone reacts with impurity (e.g., silica) to form slag. In the combustion and fusion zone , all the charge melts and pig iron is obtained which purified further.

In the extraction of aluminium by HallHeroult process purified Al₂O₃ is mixed with CaF₂ to lower the melting point by Al₂O₃ and increase the conductivity of molten mixture

For each of produced, about of carbon anode is burnt away.

In Hall-Heroult process for extraction of aluminium (crude) from alumina (Al₂O₃).
Statements (1), (2) and (3) are correct because cryolite (Na₃AlF₆) is added to Al₂O₃ to lower, its melting point. Here, steel vessel with lining of carbon acts as cathode and graphite acts as anode, but statement (4) is incorrect because Al gets deposited at cathode.