`ZnCl_(2)` reacts with excess of `NH_(3)` solution to produce

Options

A. A ppt of `Zn(OH)_(2)`
B. A complex ion `Zn(OH)_(4)^(2-)` of tetrahedral geometry
C. A complex ion `Zn(NH_(3))_(4)^(2+)` of tetrahedral geometry
D. A complex ion `Zn(NH_(3))_(4)^(2+)` of square planar geometry

Answer

To solve the question of what happens when ZnCl₂ reacts with excess NH₃ solution, we can follow these steps:

### Step 1: Identify the Reactants
We have zinc chloride (ZnCl₂) and ammonia (NH₃) as reactants.

### Step 2: Understand the Reaction
When ZnCl₂ reacts with an excess of NH₃, it forms a complex. Ammonia acts as a ligand and coordinates to the zinc ion.

### Step 3: Write the Reaction
The reaction can be represented as:
\[ \text{ZnCl}_2 + 4 \text{NH}_3 \rightarrow \text{[Zn(NH}_3\text{)}_4]^{2+} + 2 \text{Cl}^- \]

### Step 4: Determine the Charge of the Complex
Zinc typically has a +2 oxidation state in ZnCl₂, and since it forms a complex with four neutral NH₃ molecules, the overall charge of the complex ion is +2.

### Step 5: Identify the Complex Ion
The complex ion formed is \([Zn(NH_3)_4]^{2+}\).

### Step 6: Determine the Geometry of the Complex
To determine the geometry, we need to consider the hybridization of the central metal ion (Zn²⁺).

- Zinc in its elemental form has the electron configuration of [Ar] 3d¹⁰ 4s².
- When it loses two electrons to become Zn²⁺, its configuration becomes 3d¹⁰.
- The coordination number of the complex is 4 (due to 4 NH₃ ligands), which suggests sp³ hybridization.

### Step 7: Identify the Shape
The sp³ hybridization leads to a tetrahedral geometry for the complex \([Zn(NH_3)_4]^{2+}\).

### Final Answer
Thus, when ZnCl₂ reacts with excess NH₃, it produces the complex \([Zn(NH_3)_4]^{2+}\) with tetrahedral geometry.

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