In oxidation of oxalic acid by `KMnO_(4)`, the colour of `KMnO_(4)` disappears slowly in the start of reaction but disappears very fast afterwards. This is an example of :-

Options

A. Auto catalysis
B. Negative catalysis
C. Induced catalysis
D. Positive catalysis

Answer

To solve the question regarding the oxidation of oxalic acid by KMnO4, we will analyze the reaction and determine the reason for the color change of KMnO4 during the reaction.

### Step-by-Step Solution:

1. **Identify the Reaction**:
The reaction involves oxalic acid (C2O4^2-) being oxidized by potassium permanganate (KMnO4) in an acidic medium (H+ ions). The overall reaction can be written as:
\[ C_2O_4^{2-} + KMnO_4 + H^+ \rightarrow Mn^{2+} + H_2O + CO_2 \]

2. **Balance the Reaction**:
To balance the reaction, we need to ensure that the number of atoms of each element and the charge are the same on both sides. The balanced reaction can be represented as:
\[ 5C_2O_4^{2-} + 2KMnO_4 + 16H^+ \rightarrow 2Mn^{2+} + 8H_2O + 10CO_2 \]

3. **Color Change Observation**:
In this reaction, KMnO4 is purple in color due to the presence of MnO4^- ions. As the reaction proceeds, these MnO4^- ions are reduced to colorless Mn^2+ ions. Initially, the disappearance of color is slow because the concentration of oxalic acid is relatively high, and the reaction rate is low.

4. **Understanding the Fast Disappearance**:
As the reaction progresses, the concentration of oxalic acid decreases, and the reaction rate increases due to the formation of products that can catalyze the reaction. This phenomenon is known as **autocatalysis**, where one of the products of the reaction (in this case, CO2) acts as a catalyst to speed up the reaction.

5. **Conclusion**:
Therefore, the color of KMnO4 disappears slowly at first and then rapidly as the reaction proceeds, indicating that this is an example of an **autocatalytic reaction**.

### Final Answer:
This is an example of **autocatalysis**.