Which of the following is a highly corrosive salt?

Options

A. `Hg_2Cl_2`
B. `HgCl_2`
C. `FeCl_2`
D. `PbCl_2`

Answer

To determine which of the given salts is highly corrosive, we need to analyze the oxidation states and the ability of these salts to accept electrons. Let's break down the steps involved in solving this question.

### Step-by-Step Solution:

1. **Understand Corrosive Salts**:
- Corrosive salts are typically those that can accept electrons easily. This means they have a tendency to undergo reduction.

2. **Identify the Options**:
- The options provided are:
- Hg2Cl2 (Mercurous chloride)
- HgCl2 (Mercuric chloride)
- FeCl2 (Iron(II) chloride)
- PbCl2 (Lead(II) chloride)

3. **Analyze the Oxidation States**:
- For Hg2Cl2, mercury is in the +1 oxidation state.
- For HgCl2, mercury is in the +2 oxidation state.
- For FeCl2, iron is in the +2 oxidation state.
- For PbCl2, lead is in the +2 oxidation state.

4. **Determine Stability and Electron Donation**:
- The higher the oxidation state of a metal, the more stable it is in that state and the less likely it is to donate electrons.
- HgCl2 has mercury in the +2 state, which means it has a filled electronic configuration (Xe 4f14 5d10 6s2). This stability means it is less likely to donate electrons and more likely to accept them.

5. **Comparison of Corrosiveness**:
- Between Hg2Cl2 and HgCl2, HgCl2 is more corrosive because it is in a higher oxidation state (+2) compared to Hg2Cl2 (+1).
- FeCl2 and PbCl2 are less corrosive compared to mercury salts due to their lower oxidation states and stability.

6. **Conclusion**:
- Based on the analysis, HgCl2 (Mercuric chloride) is identified as the highly corrosive salt.

### Final Answer:
The highly corrosive salt is **HgCl2 (Mercuric chloride)**.

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