_____acts as an acidic flux while_____acts as a basic flux.

Answer

To answer the question regarding which substances act as acidic and basic fluxes, we can break down the solution into the following steps:

### Step-by-Step Solution:

1. **Understanding Flux**:
- Flux is a substance that is added to ores to help remove impurities (gangue) during the extraction of metals. It combines with the gangue to form a slag, which can be easily removed.

2. **Identifying Acidic and Basic Fluxes**:
- Fluxes can be classified into two categories: acidic fluxes and basic fluxes.
- Acidic fluxes are used to remove basic gangue, while basic fluxes are used to remove acidic gangue.

3. **Examples of Acidic and Basic Fluxes**:
- **Acidic Flux**: Silica (SiO2) is a common example of an acidic flux. It is used to remove basic impurities such as iron oxide (FeO).
- **Basic Flux**: Calcium oxide (CaO) is an example of a basic flux. It is used to remove acidic impurities like silica.

4. **Final Answer**:
- Therefore, the complete answer to the question is: **Silica (SiO2) acts as an acidic flux while Calcium oxide (CaO) acts as a basic flux.**