Which of the following statement(s) is/are correct?

Options

A. `S_(2)O_(3)^(2-)` oxidised `Ag^(+)` in presence of pyridine and give red colour compound
B. `MnO_(4)^(2-)` disproportionates to yield `MnO_(4)^(-)` in presence of `H^(+)` ions.
C. In `Cr_(2)O_(7)^(2-)` each `Cr` is linked to four oxygen atoms.
D. `Ti^(3+)` is purple while `Ti^(4+)` is colourless.

Explanation

To determine which of the statements regarding the D-block elements are correct, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Analyzing Statement A**:
- The statement claims that H2O3-2 oxidizes Ag+ in the presence of pyridine to give a red color compound.
- Upon investigation, we find that H2O3-2 (hypo) does not oxidize Ag+. Instead, it forms a soluble complex with Ag+, which is Na3AgS2O3, and AgBr is formed as a byproduct.
- **Conclusion**: This statement is **false**.

2. **Analyzing Statement B**:
- The statement claims that MnO4-2 disproportionates to yield MnO4- in the presence of H+ ions.
- This is indeed correct. In an acidic medium, K2MnO4 can disproportionate to form KMnO4 and MnO2. The oxidation states change from +6 in MnO4-2 to +7 in MnO4- and +4 in MnO2.
- **Conclusion**: This statement is **true**.

3. **Analyzing Statement C**:
- The statement claims that in Cr2O7-2 (dichromate ion), each Cr is linked to 4 oxygen atoms.
- The structure of the dichromate ion shows that each chromium atom is indeed surrounded by 4 oxygen atoms (three of which are in a double bond and one in a single bond).
- **Conclusion**: This statement is **true**.

4. **Analyzing Statement D**:
- The statement claims that Ti+3 is purple whereas Ti+4 is colorless.
- The electronic configuration of Ti+3 is 3d1, which has one unpaired electron and can absorb light, resulting in a color (purple). In contrast, Ti+4 has a 3d0 configuration, meaning it has no unpaired electrons and is colorless.
- **Conclusion**: This statement is **true**.

### Final Answer:
The correct statements are **B, C, and D**.

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