`Hg_2Cl_2` + `NH_4OH` `to`

Answer

To solve the question regarding the reaction of `Hg2Cl2` (mercury(I) chloride) with `NH4OH` (ammonium hydroxide), we can break it down into a step-by-step text solution.

### Step-by-Step Solution:

1. **Identify the Reactants**:
The reactants in this reaction are `Hg2Cl2` and `NH4OH`.

2. **Understand the Reaction**:
When `Hg2Cl2` reacts with `NH4OH`, it forms a complex compound along with other products. This is a common reaction in inorganic chemistry.

3. **Write the Products**:
The main product formed is a complex compound known as Amido mercuric chloride. The reaction can be summarized as follows:
- The complex compound formed is `HgO.Hg(NH2Cl)`, which is a black precipitate.
- Along with this, elemental mercury (`Hg`) and ammonium chloride (`NH4Cl`) are produced.

4. **Balance the Reaction**:
The balanced chemical equation for the reaction is:
\[ 2Hg_2Cl_2 + 4NH_4OH \rightarrow 2HgO.Hg(NH_2Cl) + 3NH_4Cl + 3H_2O \]

5. **Identify the Nature of the Precipitate**:
The precipitate formed, Amido mercuric chloride, is characterized as a black solid.

6. **Excess NH4OH Reaction**:
If excess `NH4OH` is added to the precipitate, it remains insoluble, which is an important observation in this reaction.

### Final Products:
- The main products of the reaction are:
- Amido mercuric chloride (black precipitate)
- Mercury (Hg)
- Ammonium chloride (NH4Cl)
- Water (H2O)