Select the correct statement(s) :

Options

A. When `T rarr oo ` or `E_(a)rarr O` then K=A
B. A positive catalyst can change `DeltaH` of the reaction
C. A mixture catalyst may be thermodynamically unstable by kinetically stable
D. A negative catalyst increases the activation energy of the reaction

Answer

To solve the question, we need to analyze each statement provided and determine whether it is correct or incorrect based on our understanding of chemical kinetics and catalysis.

### Step-by-Step Solution:

1. **Statement Analysis**:
- **Statement A**: "When t is infinite or Ea, then k is equal to A."
- The Arrhenius equation states that \( k = A e^{-\frac{E_a}{RT}} \). As temperature \( T \) approaches infinity, the term \( e^{-\frac{E_a}{RT}} \) approaches 1, thus \( k \) approaches \( A \). This statement is **correct**.

2. **Statement B**: "A positive catalyst can change ΔH of the reaction."
- Catalysts lower the activation energy of a reaction but do not change the overall enthalpy change (ΔH) of the reaction. Therefore, this statement is **incorrect**.

3. **Statement C**: "A mixture catalyst may be thermodynamically unstable but kinetically stable."
- A mixture of reactants can be thermodynamically unstable if the products are favored at equilibrium, but it can be kinetically stable if the reaction rate is very slow under certain conditions. For example, coal and oxygen are stable until heated. This statement is **correct**.

4. **Statement D**: "A negative catalyst increases the activation energy of the reaction."
- A negative catalyst (or inhibitor) works by increasing the activation energy, making the reaction slower. This statement is **correct**.

### Conclusion:
- The correct statements are A, C, and D.

### Final Answer:
- **Correct Statements**: A, C, D