When sulphur dioxide () gas is used as a bleaching agent in the presence of moisture, its bleaching — p Block Elements Chemistry Question

💡 Solution & Explanation

$SO_2$ bleaches colored organic matter by reducing it to a colorless leuco compound in the presence of moisture ($SO_2 + 2H_2O \rightarrow H_2SO_4 + 2[H]$). Because it operates via reduction, the bleaching effect is temporary and can be reversed by aerial oxidation.