Question

The flux is used in the extraction of iron from haematite in the blast furnace is:
A. silica
B. Limestone
C. Phosphorus chloride
D. Calcium phosphate

Answer 1

Hint: Haematite is an ore from which the iron metal is extracted but along with the iron other impurities are also present. So, flux used will combine with the impurity and form slag. The flux used is a carbonate of the atom with atomic no. 20.

Complete Step-by-Step Answer:
- In the given question, we have to identify the correct flux which is used in the extraction of iron from the haematite in the blast furnace.
- Haematite is also known as red oxide of iron.
- To extract iron from the haematite, it undergoes the process of concentration, calcination, smelting.
- In concentration, the ore is converted into the powdered form from the solid form by crushing. Then it is washed by the water and the heavy particles of the ore will settle down.
- Now, in calcination, the concentrated ore is heated in the presence of air to drive out the moisture and expel the impurities such as sulphur, arsenic and phosphorus.
- In smelting, the reduction of the ore with carbon takes place in the blast furnace.
- The blast furnace is made up of steel and fire-resistant bricks.
- Now, in the blast furnace the calcined ore, coke and limestone are added in which coke works as fuel and limestone is used as a flux.
- So, the function of limestone is that firstly it will decompose and yield calcium oxide.
- Now, the calcium oxide will combine with silica that is impure and forms slag. Due to which it can be removed easily.
\[\begin{align}
  & \text{CaC}{{\text{O}}_{3}}\text{ }\to \text{ CaO + C}{{\text{O}}_{2}} \\
 & \text{CaO + Si}{{\text{O}}_{2}}\text{ }\to \text{ CaSi}{{\text{O}}_{3}} \\
\end{align}\]

Therefore, option B is the correct answer.

Note: In the given question, flux is a type of cleansing agent because it helps remove the impurity of silica from the haematite. Fluxes which are highly reactive are mainly corrosive and acidic. Flux is made up of four things i.e. activators, vehicles, solvents and additives.