Question

The correct statement is:
(A) Leaching of Bauxite using concentrated NaOH solution gives sodium aluminate and sodium silicate
(B) The blistered appearance of copper during the metallurgical process is due to the evolution of $C{O_2}$
(C) Pig iron is obtained from cast iron
(D) The Hall-Heroult process is used for the production of aluminum and iron

Answer 1

Hint:. The Hall-Heroult process is an electrolysis process. In the leaching of Bauxite, the reaction of ore with concentrated NaOH solution is also called digestion. Blistered appearance of copper is due to the evolution of a gas which is also responsible for acid rain.

Complete step by step answer:
We will take a look at all the statements in order to find which one is true.
A) In the process of leaching of Bauxite, the ore is heated with a concentrated solution of NaOH at 473K to 523K temperatures. This process is often called digestion. The ore also contains $Si{O_2}$ alongside iron oxides and titanium oxides. Thus, Sodium aluminate is formed as a product. The reaction can be given as
     \[A{l_2}{O_{2(s)}} + 2NaO{H_{(aq)}} + 3{H_2}{O_{(l)}} \to 2Na{[Al{(OH)_4}]_{(aq)}}\]

- Here, Silica dissolves in order to form sodium silicate. Thus, this statement is true.

B) The Copper matte is charged into a silica lined converter in order to obtain metallic copper. The reaction of obtaining metallic copper can be given as
     \[2C{u_2}O + C{u_2}S \to 6Cu + S{O_2}\]

Here, the copper obtained has a characteristic blistered appearance. This is due to the evolution of sulphur dioxide gas. Thus, the given statement is not true.

C) The iron which is obtained from blast furnaces and contains about 4% carbon and other impurities is called pig iron. When pig iron is melted with scrap iron and coke in presence of hot air, cast iron is obtained. Thus, cast iron is obtained from pig iron. So, the statement given in the option is not true.

D) Hall-Heroult process is an electrolysis process by which we can obtain aluminum from alumina. It is not used to obtain iron. Thus, the statement given in option is not true.
So, the correct answer is “Option A”.

Note: Remember that cast iron has slightly lower content of carbon in its structure which is around 3%. it is extremely brittle and hard. Wrought iron is the purest form of iron. It is a malleable form of iron.