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

Options

A. The stability constant of `[Co(H_(2)O)_(6)]^(3+)` is larger than that of `[Co(H_(2)O)_(6)]^(2+)`
B. The cyano complexes more stable than those formed by halide ions .
C. The stability of halide complexes follows the order `I^(Θ)gtBr^(Θ)gtCI^(Θ)gtF^(Θ)` .
D. The stability constant of `[Co(NH_(3))_(4)]^(2+)` is less than that of `[CuCI_(4)]^(2-)` .

Answer

To determine which statements regarding coordination compounds are correct, we will analyze each option step by step.

### Step 1: Analyze Option 1
**Statement:** The stability constant of cobalt H₂O₆³⁺ is larger than the stability of cobalt H₂O₆²⁺ complex.

**Explanation:**
- The stability of a complex ion is influenced by the oxidation state of the central metal ion.
- Cobalt in the +3 oxidation state (Co³⁺) has a higher charge compared to cobalt in the +2 oxidation state (Co²⁺).
- The stability of a complex is directly proportional to the charge on the central metal ion. Therefore, Co³⁺ will form a more stable complex than Co²⁺.

**Conclusion:** Option 1 is correct.

### Step 2: Analyze Option 2
**Statement:** The cyanocomplex is more stable than those formed by halide ions.

**Explanation:**
- The stability of a complex is also related to the basicity of the ligands involved.
- Cyanide (CN⁻) is a stronger field ligand compared to halide ions (like Cl⁻, Br⁻, I⁻).
- Since cyanide is more basic than halide ions, complexes formed with cyanide will be more stable than those formed with halides.

**Conclusion:** Option 2 is correct.

### Step 3: Analyze Option 3
**Statement:** The stability of halide complexes follows the order iodide-bromide-chloride-fluoride.

**Explanation:**
- The stability of halide complexes is inversely related to the basicity of the halide ions.
- The correct order of stability based on basicity is: F⁻ > Cl⁻ > Br⁻ > I⁻.
- Thus, the stability of the complexes should follow the order: fluoride > chloride > bromide > iodide, which contradicts the given statement.

**Conclusion:** Option 3 is incorrect.

### Step 4: Analyze Option 4
**Statement:** The stability constant of cobalt ammoniac complex (Co²⁺) is less than the copper chloride complex.

**Explanation:**
- For Co²⁺, the electronic configuration is d⁷, and for Cu²⁺, it is d⁹.
- Generally, more d-electrons lead to less stability due to electron-electron repulsion.
- Therefore, the cobalt complex (Co²⁺) is expected to be more stable than the copper chloride complex (Cu²⁺).

**Conclusion:** Option 4 is incorrect.

### Final Conclusion
The correct statements are:
- Option 1: Correct
- Option 2: Correct
- Option 3: Incorrect
- Option 4: Incorrect

Thus, the answer is that only options 1 and 2 are correct.

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