Question

The flux used in the preparation of wrought iron from cast iron in reverberatory furnace is:

• A. SiO\(_2\)
• B. CaCO\(_3\)
• C. C
• D. NaCN

Hint:

Calcium carbonate (\(CaCO_3\)) acts as a flux to remove acidic impurities such as silica (\(SiO_2\)) in metallurgy.

Answer 1

The Correct Option is B

Step 1: Understanding Flux in Iron Extraction 
- Flux is a substance used in metallurgy to remove impurities by forming slag. 
- In wrought iron production, the impurities (SiO\(_2\)) are removed using CaCO\(_3\) (Limestone) as a flux.
Step 2: Reaction Involved \[ CaCO_3 \rightarrow CaO + CO_2 \] \[ CaO + SiO_2 \rightarrow CaSiO_3 \text{ (Slag)} \]
Step 3: Explanation 
- SiO\(_2\) is an impurity, not a flux.
- C (carbon) is used as a reducing agent.
- NaCN is not used in iron metallurgy. 
Thus, the correct answer is CaCO\(_3\).

Answer 2

In the preparation of wrought iron from cast iron in a reverberatory furnace, a flux is added to remove impurities such as silica (SiO₂).

Cast iron contains impurities like carbon, silicon, phosphorus, and sulfur. During the refining process, these impurities must be removed to obtain the relatively pure form of iron known as wrought iron.

Calcium carbonate (CaCO₃), commonly known as limestone, is used as a flux in this process. When heated in the furnace, CaCO₃ decomposes to form calcium oxide (CaO):

CaCO₃ → CaO + CO₂

The calcium oxide (CaO) formed acts as the actual flux. It reacts with acidic impurities such as silica to form calcium silicate (CaSiO₃), which floats as slag and can be easily removed:

CaO + SiO₂ → CaSiO₃ (slag)

This helps in purifying the iron and converting cast iron into wrought iron.

Therefore, the flux used is:
CaCO₃