Mercuric chloride is converted into mercury by:

Options

A. placing copper metal in aqueous solution of `HgCl_(2)`
B. treating aqueous solution of `HgCl_(2)` with excess of stannous chloride
C. treating aqueous solution `HgCl_(2)` with `PbCl_(2)` solution
D. None of these

Answer

To convert mercuric chloride (HgCl2) into mercury (Hg), we can follow a two-step process:

### Step 1: Reaction with Copper
1. **Place Copper Metal in Aqueous Solution of HgCl2**:
- When copper metal (Cu) is added to an aqueous solution of mercuric chloride (HgCl2), a reaction occurs where copper displaces mercury from the mercuric chloride.
- The balanced chemical equation for this reaction is:
\[ 2 \text{Cu} + \text{HgCl}_2 \rightarrow 2 \text{CuCl} + \text{Hg} \]
- In this reaction, copper (Cu) is oxidized to copper(I) chloride (CuCl), and mercury (Hg) is reduced to its elemental form.

### Step 2: Reaction with Stannous Chloride
2. **Treating Aqueous Solution of HgCl2 with Excess Stannous Chloride (SnCl2)**:
- In the second step, we take the aqueous solution of mercuric chloride (HgCl2) and treat it with excess stannous chloride (SnCl2).
- The reaction can be represented as:
\[ \text{HgCl}_2 + \text{SnCl}_2 \rightarrow \text{Hg}_2\text{Cl}_2 + \text{SnCl}_4 \]
- Here, mercuric chloride is reduced to mercurous chloride (Hg2Cl2), while stannous chloride is oxidized to stannic chloride (SnCl4).

3. **Reduction of Mercurous Chloride**:
- The mercurous chloride (Hg2Cl2) formed in the previous step can then be reduced to metallic mercury (Hg) by reacting it with excess stannous chloride:
\[ \text{Hg}_2\text{Cl}_2 + 2 \text{SnCl}_2 \rightarrow 2 \text{Hg} + 2 \text{SnCl}_4 \]
- This final reaction produces elemental mercury and stannic chloride.

### Final Summary:
Thus, the overall process to convert mercuric chloride to mercury involves:
1. Placing copper in an aqueous solution of HgCl2 to produce mercury and copper(I) chloride.
2. Treating the resulting solution with excess stannous chloride to produce mercurous chloride, which is then further reduced to metallic mercury.