The coordination number of `Ni^(2+)` is 4
`NiCI_(2) + KCN` (excess)rarr`A` (cyano complex)
`NiCI_(2)+conc.HCI` (excess) rarr `B` (Chloro complex)
The `IUPAC` name of `A` and `B` are .

Options

A. potassium tetracyanonickelate(II),potassium tetrachloronickelate(II) .
B. tetracyanopotassiumnickelate(II)tetrrachloropotassiumnickelate(II) .
C. tetracyanonickel(II) tetrachloronickel(II)
D. potassium tetracyanonickel(II),tetracholoronickel(II) .

Explanation

To determine the IUPAC names of the coordination complexes formed from the reactions of `NiCl2` with `KCN` and `conc. HCl`, we will follow these steps:

### Step 1: Identify the Complex Formed with KCN
When `NiCl2` reacts with an excess of `KCN`, it forms a cyano complex. The nickel ion in this case has a coordination number of 4, and each cyanide ion (CN^-) acts as a bidentate ligand.

**Complex A:** The formula for the complex formed is `Ni(CN)4^2-`.

### Step 2: Determine the IUPAC Name for Complex A
The IUPAC naming convention for coordination compounds states that the ligands are named first followed by the metal. The prefix for four ligands is "tetra." The oxidation state of nickel in this complex is +2.

Thus, the IUPAC name for Complex A is:
**Tetra-cyano-nickel(II)**.

### Step 3: Identify the Complex Formed with Conc. HCl
When `NiCl2` reacts with concentrated hydrochloric acid (HCl), it forms a chloro complex. Similar to the previous case, the coordination number remains 4.

**Complex B:** The formula for the complex formed is `NiCl4^2-`.

### Step 4: Determine the IUPAC Name for Complex B
Following the same naming convention, the prefix for four ligands is "tetra." The oxidation state of nickel in this complex is also +2.

Thus, the IUPAC name for Complex B is:
**Tetra-chloro-nickel(II)**.

### Final Answer
The IUPAC names of the complexes are:
- Complex A: **Tetra-cyano-nickel(II)**
- Complex B: **Tetra-chloro-nickel(II)**

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