Question

The flux used in extraction of iron from haematite is

• A. \(CaCO_3\)
• B. \(SiO_2\)
• C. \(P_2O_5\)
• D. \(CaSiO_3\)

Answer 1

The Correct Option is A

To determine the flux used in the extraction of iron from hematite, we need to understand the process of iron extraction and the role of fluxes.

1. Understanding Iron Extraction:
Iron is extracted from its ores (such as hematite, $\text{Fe}_2\text{O}_3$) through a process called smelting, which typically occurs in a blast furnace. During this process, impurities such as silica ($\text{SiO}_2$) are present in the ore. To remove these impurities and facilitate the extraction of pure iron, a flux is added.

2. Role of Flux:
A flux is a substance that helps lower the melting point of impurities and forms a slag, which can be easily separated from the molten iron. The most commonly used flux in the extraction of iron is **limestone** ($\text{CaCO}_3$), which decomposes into calcium oxide ($\text{CaO}$) at high temperatures:

$$ \text{CaCO}_3 \xrightarrow{\text{High Temperature}} \text{CaO} + \text{CO}_2 $$ The calcium oxide ($\text{CaO}$) then reacts with silica ($\text{SiO}_2$) to form calcium silicate ($\text{CaSiO}_3$), which is the slag: $$ \text{CaO} + \text{SiO}_2 \rightarrow \text{CaSiO}_3 $$ This slag is less dense than molten iron and floats on top, allowing it to be removed.

3. Evaluating the Options:
Let us evaluate the given options:

1. $\text{CaCO}_3$ (Limestone): As explained above, limestone is the primary flux used in the extraction of iron. It reacts with silica to form slag, making it the correct choice.
2. $\text{SiO}_2$ (Silica): Silica is an impurity found in the ore, not a flux. It is actually one of the substances that needs to be removed using a flux.
3. $\text{P}_2\text{O}_5$ (Phosphorus Pentoxide): This compound is not used as a flux in iron extraction. It is unrelated to the process.
4. $\text{CaSiO}_3$ (Calcium Silicate): This is the slag formed as a result of the reaction between $\text{CaO}$ and $\text{SiO}_2$, but it is not the flux itself.

4. Conclusion:
The flux used in the extraction of iron from hematite is $\text{CaCO}_3$ (limestone).

Final Answer: $ {\text{CaCO}_3} $