Select the correct statements (Ellingham diagram) :

Options

A. When temperature is raised, a point will be reached where the graph crosses the `Delta_(f) G^(Ө) = 0` line. Below this temperature, the free energy of formation of the oxide is negative, so the oxide is stable
B. When the temperature is raised, a point will be reached where the graph crosses the `Delta_(f) G^(Ө) = 0` line. Above this temperature, the free energy of formation of the oxide is positive, and the oxide becomes instable, and should decompose into the metal and dioxygen.
C. Theoretically, all oxides can be decomposed to give the metal and dioxygen if a sufficiency high temperature can be attained.
D. Theoretically, all oxides cannot be decomposed to give the metal and dioxide if a sufficiently high temperature can be attained.

Answer

### Step-by-Step Solution:

1. **Understanding the Ellingham Diagram**:
- The Ellingham diagram is a graphical representation that plots the standard Gibbs free energy change (ΔG°) of a reaction against temperature (T). It is used to predict the stability of metal oxides and the feasibility of reduction reactions.

2. **Identifying Key Features**:
- In the diagram, the line where ΔG = 0 indicates the temperature at which the formation of the oxide is neither favorable nor unfavorable. Below this line, the formation of the oxide is stable (ΔG < 0), and above this line, the oxide is unstable (ΔG > 0).

3. **Evaluating the Statements**:
- **Option 1**: The oxide is stable below the ΔG = 0 line. This is correct because it indicates that the formation of the oxide is favored at lower temperatures.
- **Option 2**: When the temperature is raised above the ΔG = 0 line, the free energy of formation of the oxide becomes positive, indicating instability. This is also correct.
- **Option 3**: Theoretically, if a sufficiently high temperature is reached, the oxide can decompose to give the metal and oxygen. This statement is correct as well, since high temperatures can provide the energy needed for decomposition.
- **Option 4**: The statement that theoretically all oxides cannot be decomposed is incorrect. While some oxides may be difficult to decompose practically, theoretically, many can be decomposed under the right conditions.

4. **Conclusion**:
- Based on the evaluation, the correct statements are Options 1, 2, and 3.

### Final Answer:
The correct statements about the Ellingham diagram are Options 1, 2, and 3.

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