Compound that is both paramagnetic and coloured is:

Options

A. 1. `K_2Cr_2O_7`
B. 2. `(NH_4)_2[TiCl_6]`
C. 3. `VOSO_4`
D. 4. `K_3[Cu(CN)_4]`

Explanation

To determine which compound is both paramagnetic and colored, we need to analyze the given options based on their electronic configurations and oxidation states. Here’s a step-by-step solution:

### Step 1: Understand the Criteria for Color and Paramagnetism
- **Color**: A compound is colored if it has an incomplete d-subshell. Transition metal complexes with incomplete d-subshells can absorb visible light, leading to color.
- **Paramagnetism**: A compound is paramagnetic if it has unpaired electrons in its d-subshell. This occurs when there are incomplete d-orbitals.

### Step 2: Analyze Each Option
We will analyze the oxidation states and electronic configurations of each compound provided in the options.

#### Option A: K2Cr2O7
- **Oxidation State of Cr**: +6
- **Electronic Configuration**: Cr^6+ has the configuration [Ar] 3d^0.
- **Conclusion**: Since it has a d^0 configuration (empty d-subshell), it is colorless and not paramagnetic.

#### Option B: NH4TiCl6
- **Oxidation State of Ti**: +4
- **Electronic Configuration**: Ti^4+ has the configuration [Ar] 3d^0.
- **Conclusion**: Similar to Option A, it has a d^0 configuration (empty d-subshell), making it colorless and not paramagnetic.

#### Option C: VOSO4
- **Oxidation State of V**: +4
- **Electronic Configuration**: V^4+ has the configuration [Ar] 3d^1.
- **Conclusion**: This has an incomplete d-subshell (3d^1), indicating it is colored and paramagnetic due to the presence of one unpaired electron.

#### Option D: K3Cu(CN)4
- **Oxidation State of Cu**: +1
- **Electronic Configuration**: Cu^1+ has the configuration [Ar] 3d^10.
- **Conclusion**: This has a completely filled d-subshell (3d^10), making it colorless and not paramagnetic.

### Step 3: Final Conclusion
Based on the analysis, the only compound that is both paramagnetic and colored is **Option C: VOSO4**.

### Summary of Findings
- **Option A (K2Cr2O7)**: Colorless, not paramagnetic.
- **Option B (NH4TiCl6)**: Colorless, not paramagnetic.
- **Option C (VOSO4)**: Colored, paramagnetic.
- **Option D (K3Cu(CN)4)**: Colorless, not paramagnetic.

### Final Answer
The compound that is both paramagnetic and colored is **VOSO4**.