The complex `K_(4)[Zn(CN)_(4)(O_(2))_(2)]` is oxidised into `K_(2)[Zn(CN)_(4)(O_(2))]`, then whichof the following is//are correct:

Options

A. a.Zn(II) is oxidised to Zn(IV)
B. b.magnetic moment decreases
C. c.`O-O` bond length decreases
D. d.magnetic moment remains same.

Answer

To solve the problem regarding the oxidation of the complex \( K_4[Zn(CN)_4(O_2)_2] \) to \( K_2[Zn(CN)_4(O_2)] \), we will analyze the oxidation states of zinc in both complexes and the implications for magnetic properties and bond lengths.

### Step-by-Step Solution:

1. **Identify the Components of the Complex**:
- The first complex is \( K_4[Zn(CN)_4(O_2)_2] \).
- The second complex is \( K_2[Zn(CN)_4(O_2)] \).
- The cationic part is potassium (K) and the anionic part is the complex ion.

2. **Calculate the Oxidation State of Zinc in the First Complex**:
- Let the oxidation state of zinc be \( X \).
- The cyanide ion (CN) has a charge of -1, and there are 4 cyanide ions: \( 4 \times (-1) = -4 \).
- The peroxide (O2) has a charge of -1, and there are 2 peroxide ions: \( 2 \times (-1) = -2 \).
- The overall charge of the complex ion is -2 (since it balances with 4 K+ ions).
- Therefore, the equation is:
\[ X + (-4) + (-2) = -2 \]
\[ X - 6 = -2 \implies X = +4 \]

3. **Calculate the Oxidation State of Zinc in the Second Complex**:
- Again, let the oxidation state of zinc be \( X \).
- The cyanide ions contribute -4 (same as before).
- The oxygen here is not in the peroxide form and has a charge of 0.
- The overall charge of the complex ion is -2 (since it balances with 2 K+ ions).
- Therefore, the equation is:
\[ X + (-4) + 0 = -2 \]
\[ X - 4 = -2 \implies X = +2 \]

4. **Analyze the Change in Oxidation State**:
- In the first complex, zinc is in the +4 oxidation state, and in the second complex, it is in the +2 oxidation state.
- This indicates a change in oxidation state from +4 to +2.

5. **Determine the Magnetic Properties**:
- The electronic configuration of zinc in +2 oxidation state is \( [Ar] 3d^{10} \).
- Since the oxidation state of zinc changes from +4 to +2, the number of unpaired electrons also changes.
- In +4 state, zinc has no unpaired electrons, whereas in +2 state, it still has no unpaired electrons.
- Therefore, the magnetic moment remains unchanged.

6. **Evaluate the Bond Length**:
- In the first complex, there is a peroxide bond (O-O) which has a bond order of 1.
- In the second complex, the oxygen is in a normal bond which has a bond order of 2.
- Since bond length is inversely proportional to bond order, as bond order increases, bond length decreases.

### Conclusion:
Based on the analysis:
- The oxidation state of zinc changes from +4 to +2.
- The magnetic moment remains unchanged due to no unpaired electrons.
- The bond length of the O-O bond decreases due to an increase in bond order.

### Correct Statements:
- The magnetic moment remains the same.
- The bond length decreases.