Question

a statue coated with chemical substance X on long exposure to polluted atmosphere becomes black. the color can be restored by treatment with Hydrogen Peroxide. Identify element x and also the type of chemical change involved ​

Answer 1

Long exposure to atmosphere converts white lead into black PbS due to H2S present in the atmosphere. As a result, statues turn black.

PbO + H2S ------> PbS + H2O

On treatment with H2O2, the black PbS get oxidized to white PbSO4 and the colour is restored.

PbS + 4H2O2 --------> PbSO4 + 4H2O