old oil paintings get black and over the years due to reaction with pollutant gases in the air. give the formula of the black substance formed?
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Explanation:
When the old oil painting are kept in the atmostphere for a long period, the traces of H2S gas present in the atmosphere converts lead oxide (PbO) into lead sulphide (PbS) which is black is colour. Therefore, these paintings get transhed. The original whiteness can be restored by keeping then in hydrogen peroxide solution for sometime as a result of which lead sulphide is oxidised to lead sulphate.
PbSBlack+4H2O2→PbSO4white+4H2O
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Answer:
When an oil painting is constantly exposed to the atmosphere, the traces of hydrogen sulphide gas present in the atmosphere slowly blackens the painting by converting lead oxide (white) to lead sulphide (black).
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