Old oil paintings utilizing "White Lead" pigments often turn black over centuries due to atmospheric — Hydrogen Chemistry Question
Question
Old oil paintings utilizing "White Lead" pigments often turn black over centuries due to atmospheric $H_2S$ forming Lead Sulphide ($PbS$). Dilute $H_2O_2$ is used by art restorers to recover the original white color. What is the specific role of $H_2O_2$ and the final white product formed in this reaction?
Answer: C
💡 Solution & Explanation
Hydrogen peroxide is a powerful oxidant. It oxidizes the black Lead Sulphide ($PbS$) into Lead Sulphate ($PbSO_4$), which is white, safely restoring the painting without destroying the pigment matrix. The reaction requires exactly 4 moles of $H_2O_2$: $PbS + 4H_2O_2 \rightarrow PbSO_4 + 4H_2O$.
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