The true statement among these is:

Options

A. A positive catalyst increases the rate constant of a reaction.
B. During the course of a reaction, specific reaction rate remains constant.
C. Rate constant always increases with rise in temperature whether the reaction is endothermic or exothermic.
D. All of these are correct

Answer

To determine the true statement among the given options, we will analyze each statement one by one.

### Step 1: Analyze Statement A
**Statement A:** Positive catalysts increase the rate of the reaction.

- **Explanation:** A positive catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. It does this by providing an alternative reaction pathway with a lower activation energy. This means that both the forward and reverse reactions are accelerated, allowing the system to reach equilibrium more quickly.

**Conclusion:** Statement A is true.

### Step 2: Analyze Statement B
**Statement B:** During the course of the reaction, a specific reaction rate remains constant.

- **Explanation:** The rate of a reaction is dependent on the concentration of the reactants and can change as the reaction progresses. As reactants are consumed, their concentrations decrease, which typically results in a decrease in the reaction rate. Therefore, the reaction rate is not constant throughout the reaction.

**Conclusion:** Statement B is false.

### Step 3: Analyze Statement C
**Statement C:** The rate constant always increases with the rise in temperature, whether the reaction is endothermic or exothermic.

- **Explanation:** According to the Arrhenius equation, the rate constant (k) of a reaction increases with an increase in temperature. This is true for both endothermic and exothermic reactions, as higher temperatures provide more energy to the reactants, increasing the likelihood of successful collisions.

**Conclusion:** Statement C is true.

### Step 4: Analyze Statement D
**Statement D:** All the above statements are true.

- **Explanation:** From our analysis, we found that Statement A and Statement C are true, while Statement B is false. Therefore, not all statements are true.

**Conclusion:** Statement D is false.

### Final Conclusion
The only true statements are A and C. Since the question asks for the true statement among the options, we conclude that the correct answer is that **Statement A** and **Statement C** are true, but since D claims all are true, it is false.