Select the correct statements :

Options

A. In hydrometallurgy, `Zn` is used as oxidising agent in the purification of `Ag` from `[Ag(CN)_(2)]^(Ө)`.
B. When pine oil or eucalyptus oil is added into the water, it lowers down the surface tension by which froth is formed.
C. Sodium ethyl xanthate is used as collector
D. Basic copper carbonate or `PbSO_(4)` is concentrated by froth flotation method by using an activator.

Answer

To solve the question regarding the correct statements about hydrometallurgy and related processes, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Analyzing Option 1:**
- The statement claims that in hydrometallurgy, zinc is used as an oxidizing agent in the purification of silver from AgCN.
- In reality, zinc is used as a reducing agent in this process.
- When zinc reacts with silver cyanide (AgCN), it reduces silver ions to metallic silver while being oxidized itself.
- Therefore, **Option 1 is incorrect.**

2. **Analyzing Option 2:**
- The statement mentions that when pine oil or eucalyptus oil is added to water, it lowers the surface tension, leading to froth formation.
- This is true; in the froth flotation process, pine oil and eucalyptus oil serve as frothing agents, which help in the separation of minerals by creating a froth that carries the desired minerals to the surface.
- Hence, **Option 2 is correct.**

3. **Analyzing Option 3:**
- The statement asserts that sodium ethyl xanthate is used as a collector.
- This is accurate; sodium ethyl xanthate is indeed used as a collector in the froth flotation process, particularly for the concentration of sulfide ores.
- Therefore, **Option 3 is correct.**

4. **Analyzing Option 4:**
- The statement claims that basic copper carbonate (PbSO4) is concentrated by the froth flotation method using an activator.
- This is also true; the froth flotation method can be used for the concentration of various ores, including basic copper carbonate, often with the help of activators.
- Thus, **Option 4 is correct.**

### Final Conclusion:
The correct options are **Option 2, Option 3, and Option 4.**