Which of the following statements is NOT correct? (1) Calcium oxide reacts vigorously with water to produce lime. (2) Slaked lime slowly creates a layer of calcium nitrate on the walls during whitewashing. (3) Silver chloride is sensitive to sunlight. (4) Decomposition reactions require energy for breaking down of reactants.
Question:
Which of the following statements is NOT correct? (1) Calcium oxide reacts vigorously with water to produce lime. (2) Slaked lime slowly creates a layer of calcium nitrate on the walls during whitewashing. (3) Silver chloride is sensitive to sunlight. (4) Decomposition reactions require energy for breaking down of reactants.
Which of the following statements is NOT correct? (1) Calcium oxide reacts vigorously with water to produce lime. (2) Slaked lime slowly creates a layer of calcium nitrate on the walls during whitewashing. (3) Silver chloride is sensitive to sunlight. (4) Decomposition reactions require energy for breaking down of reactants.
Options
Answer: (2) Slaked lime slowly creates a layer of calcium nitrate on the walls during whitewashing
Explanation:
Statement (2) is incorrect. During whitewashing, slaked lime [Ca(OH)₂] is applied to walls. Over time, it reacts with carbon dioxide (CO₂) present in the air to form calcium carbonate (CaCO₃), not calcium nitrate. The reaction is: Ca(OH)₂ + CO₂ → CaCO₃ + H₂O. This layer of calcium carbonate gives the wall a shiny white finish. Statement (1) is correct — CaO + H₂O → Ca(OH)₂ is a vigorous exothermic reaction.
Explanation:
Statement (2) is incorrect. During whitewashing, slaked lime [Ca(OH)₂] is applied to walls. Over time, it reacts with carbon dioxide (CO₂) present in the air to form calcium carbonate (CaCO₃), not calcium nitrate. The reaction is: Ca(OH)₂ + CO₂ → CaCO₃ + H₂O. This layer of calcium carbonate gives the wall a shiny white finish. Statement (1) is correct — CaO + H₂O → Ca(OH)₂ is a vigorous exothermic reaction.
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