2021 · Q116
Calcium oxide reacts vigorously with water to produce slaked lime whose solution is used for white-washing walls. This slaked lime reacts with component. (A) in air to form a thin layer of component (B) to give a shiny finish. What are the components (A) and (B) ?
General KnowledgeChemistry
- AA – O ; B – CaCO 2 3
- BA – CO ; B – Ca(OH) 2 2
- CA – O ; B – Ca(OH) 2 2
- DA – CO ; B – CaCO 2 3
Explanation
Calcium oxide reacts with water to give slaked lime, Ca(OH)2; on white-washed walls this reacts with carbon dioxide (A = CO2) in the air to form a thin layer of calcium carbonate (B = CaCO3), giving the shiny finish. Oxygen is not the reactant, and the product layer is CaCO3, not Ca(OH)2. Components A and B are CO2 and CaCO3 (option D).