In a complexometric titration of metal ion with ligand
`M("Metal ion") + L("Ligand")rarr C("Complex")` end point is estimated spectrophotometrically (through light absorption). If 'M' and 'C' do not absorb light and only 'L' absorbs, then the titration plot between absorbed light(A) versus volume of ligand 'L' (V) would look like :

Options

A.
B.
C.
D.

Answer

To solve the problem, we need to analyze the behavior of the system during the complexometric titration of a metal ion (M) with a ligand (L), where the metal ion (M) and the resulting complex (C) do not absorb light, but the ligand (L) does.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
- The reaction can be represented as:
\[ M + L \rightarrow C \]
- Here, M is the metal ion, L is the ligand, and C is the complex formed.

2. **Initial Conditions**:
- At the start of the titration, only the ligand (L) is present, and it absorbs light. Therefore, the initial absorption (A) will be at its maximum because no complex (C) has formed yet.

3. **Titration Process**:
- As we add the ligand (L) to the metal ion (M), the ligand starts to react with the metal ion to form the complex (C).
- As more ligand is added, the concentration of free ligand (L) decreases because it is being converted into the complex (C).

4. **Absorption Changes**:
- Since only the ligand (L) absorbs light, as it gets converted into the complex (C), the absorption (A) will decrease initially.
- However, as the reaction progresses and more ligand is converted into the complex, the absorption will begin to increase again because the complex (C) will eventually reach a point where it is stable and does not absorb light.

5. **Endpoint of Titration**:
- At the endpoint of the titration, all the ligand (L) will have reacted with the metal ion (M) to form the complex (C).
- After reaching the endpoint, if more ligand is added, the absorption will remain constant because there will be no free ligand left to absorb light.

6. **Plotting the Graph**:
- The plot of absorbed light (A) versus the volume of ligand (V) will show an initial increase in absorption as ligand is added, followed by a plateau when the complex formation is complete.
- The graph will start at a certain absorption level, rise to a peak, and then level off as the reaction reaches completion.

### Conclusion:
The titration plot between absorbed light (A) versus volume of ligand (L) will show an initial increase followed by a plateau, indicating that the endpoint has been reached and no further increase in absorption occurs.