These questions consist of two statements each, printed as Assertion and Reason. While answering these questions you are required to choose any one of the following four responses:
Assertion: `[Ti(H_2O)_6]^(3+)` is coloured while `[Sc(H_2O)_6]^(3+)` is colourless.
Reason: d-d transition is not possible in `[Sc(H_2O)_6]^(3+)`.

Options

A. If assertion is true but the reason is false
B. If assertion is false but reason is true
C. If both assertion and reason are true and the reason is the correct explanation of assertion
D. If both assertion and reason are true but reason is not the correct explanation of assertion

Explanation

To solve the given question, we need to analyze the Assertion and Reason provided.

### Assertion:
`[Ti(H₂O)₆]^(3+)` is coloured while `[Sc(H₂O)₆]^(3+)` is colourless.

### Reason:
d-d transition is not possible in `[Sc(H₂O)₆]^(3+)`.

### Step-by-step Solution:

1. **Identify the Electronic Configurations**:
- Titanium (Ti) has an atomic number of 22. Its electronic configuration is:
\[ \text{Ti: } [Ar] 4s^2 3d^2 \]
- Scandium (Sc) has an atomic number of 21. Its electronic configuration is:
\[ \text{Sc: } [Ar] 4s^2 3d^1 \]

2. **Determine the Oxidation States**:
- In the complex `[Ti(H₂O)₆]^(3+)`, titanium is in the +3 oxidation state. This means it loses 3 electrons:
\[ \text{Ti}^{3+}: [Ar] 3d^1 \]
- In the complex `[Sc(H₂O)₆]^(3+)`, scandium is also in the +3 oxidation state. This means it loses 3 electrons:
\[ \text{Sc}^{3+}: [Ar] 3d^0 \]

3. **Color of the Complexes**:
- The color of transition metal complexes is often due to d-d transitions, which occur when electrons in the d-orbitals are excited from a lower energy level (t2g) to a higher energy level (eg).
- For `[Ti(H₂O)₆]^(3+)`, there is one electron in the 3d orbital (3d^1), which allows for d-d transitions, making the complex coloured.
- For `[Sc(H₂O)₆]^(3+)`, there are no electrons in the d-orbitals (3d^0), which means d-d transitions cannot occur, resulting in a colourless complex.

4. **Evaluate the Assertion and Reason**:
- The assertion states that `[Ti(H₂O)₆]^(3+)` is coloured while `[Sc(H₂O)₆]^(3+)` is colourless. This is **true**.
- The reason states that d-d transition is not possible in `[Sc(H₂O)₆]^(3+)`, which is also **true** since there are no d-electrons to facilitate this transition.

5. **Conclusion**:
- Both the assertion and reason are true, but the reason correctly explains why the assertion is true.

### Final Answer:
The correct response is that both the assertion and reason are true, but the reason is not the correct explanation for the assertion.