Status coated with white lead on long exposure to atmosphere turn black and the original colour can be restored on treatment with `H_(2)O_(2)` . Why ?

Explanation

### Step-by-Step Solution:

1. **Understanding the Initial Condition**:
- White lead, which is primarily lead(II) carbonate (PbCO₃) or lead(II) oxide (PbO), is initially white in color.

2. **Exposure to Atmosphere**:
- Upon long exposure to the atmosphere, especially in the presence of sulfur compounds (like hydrogen sulfide, H₂S), the white lead reacts to form lead sulfide (PbS), which is black in color.
- The reaction can be summarized as:
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