Question

In the extraction of iron using blast furnace to remove the impurity (X), chemical (Y) is added to the ore. X and Y are respectively

• A. SiO₂, MgCO₃
• B. FeO, SiO₂
• C. SiO₂, CaCO₃
• D. SiO₂, FeCO₃

Hint:

Remember the principle of slag formation: Acidic impurity + Basic flux \(\rightarrow\) Slag, or Basic impurity + Acidic flux \(\rightarrow\) Slag. For iron extraction, the impurity (SiO₂) is acidic, so the flux (CaCO₃ \(\rightarrow\) CaO) must be basic.

Answer 1

The Correct Option is C

Step 1: Identify Impurity in Iron Ore: Haematite (\( \text{Fe}_2\text{O}_3 \)) ore usually contains silica (\( \text{SiO}_2 \)) as a major acidic impurity (Gangue). So, X is \( \text{SiO}_2 \).
Step 2: Identify Flux: To remove the acidic impurity \( \text{SiO}_2 \), a basic flux is required. Limestone (\( \text{CaCO}_3 \)) is added to the blast furnace. It decomposes to form Calcium Oxide (\( \text{CaO} \)), which acts as the basic flux. \[ \text{CaCO}_3 \xrightarrow{\Delta} \text{CaO} + \text{CO}_2 \]
Step 3: Slag Formation: Flux (\( \text{CaO} \)) reacts with Gangue (\( \text{SiO}_2 \)) to form Slag (\( \text{CaSiO}_3 \)). \[ \text{CaO} + \text{SiO}_2 \to \text{CaSiO}_3 \] Thus, Y (chemical added) is \( \text{CaCO}_3 \) (Limestone).