HydrogenhardMCQ SINGLE

Old lead paintings often turn dark or black over time due to the atmospheric forming lead sulphide (Hydrogen Chemistry Question

Question

Old lead paintings often turn dark or black over time due to the atmospheric $H_2S$ forming lead sulphide ($PbS$). The original white colour of the painting can be meticulously restored using a dilute solution of $H_2O_2$. What is the exact chemical role of $H_2O_2$ in this restoration process?

Answer: B

💡 Solution & Explanation

Blackened statues and paintings are coated with $PbS$ (lead sulphide). $H_2O_2$ acts as a strong oxidizing agent, oxidizing the black $PbS$ to white $PbSO_4$ (lead sulphate), thereby safely restoring the painting's original white colour without destroying the underlying pigment. The reaction is: $PbS(s) + 4H_2O_2(aq) \rightarrow PbSO_4(s) + 4H_2O(l)$.

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