Which one of the following fluxes is used to remove acidic impurities in metallurgical processes?

Options

A. Silica
B. Sodium chloride
C. Limestone
D. Radium carbonate

Explanation

To solve the question regarding which flux is used to remove acidic impurities in metallurgical processes, we can follow these steps:

### Step 1: Understand the Concept of Flux
Flux is a substance that is added to a metallurgical process to help remove impurities. It can be either acidic or basic depending on the nature of the impurities present.

**Hint:** Remember that fluxes are used to facilitate the purification of metals by reacting with impurities.

### Step 2: Identify the Type of Impurities
In this case, the question specifies "acidic impurities." To remove acidic impurities, a basic flux is required.

**Hint:** Acidic impurities will react with basic substances to form neutral products.

### Step 3: Determine the Appropriate Basic Flux
One common basic flux used in metallurgy is limestone, which is chemically known as calcium carbonate (CaCO3). When heated, it decomposes into calcium oxide (CaO) and carbon dioxide (CO2).

**Hint:** Look for a flux that can neutralize acids; basic fluxes are typically metal oxides or carbonates.

### Step 4: Reaction of Basic Flux with Acidic Impurities
When limestone is used, the calcium oxide (CaO) produced can react with acidic impurities. For example, if phosphorus pentoxide (P4O10) is present as an acidic impurity, it can react with calcium oxide to form calcium phosphate (CaH3PO4), which is known as Thomas slag.

**Hint:** Consider the chemical reactions that occur between the flux and the impurities to understand how they neutralize each other.

### Conclusion
The flux used to remove acidic impurities in metallurgical processes is **limestone (calcium carbonate, CaCO3)**, which acts as a basic flux.

**Final Answer:** Limestone (CaCO3)