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Q92 (CDS-I/2021) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Applied everyday chemistry Answer Verified

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) ?

Result
Your answer: —  ·  Correct: D
Explanation

Calcium oxide (quicklime) reacts vigorously with water to produce slaked lime, which is calcium hydroxide [Ca(OH)2] [1]. When slaked lime is applied to walls for white-washing, it reacts slowly with component (A), carbon dioxide (CO2), present in the air [1]. This chemical reaction, known as carbonation, produces component (B), calcium carbonate (CaCO3) [1]. The reaction is represented as: Ca(OH)2(aq) + CO2(g) → CaCO3(s) + H2O(l) [1]. The thin layer of calcium carbonate formed on the walls gives them a shiny, white finish after two to three days of application. Calcium carbonate is the same chemical compound that makes up marble. Therefore, component (A) is CO2 and component (B) is CaCO3, making option 4 the correct choice.

Sources

  1. [1] Science , class X (NCERT 2025 ed.) > Chapter 1: Chemical Reactions and Equations > Figure 1.3 > p. 6
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SIMILAR QUESTIONS

CDS-II · 2023 · Q52 Relevance score: 3.75

During white-washing of walls, slaked lime reacts slowly with carbon dioxide in air to form a thin layer of calcium carbonate on the walls. Which of the following reactions represents this correctly?

CDS-I · 2023 · Q52 Relevance score: 3.64

Which of the following statements with regard to the reaction given below are correct? CaO(s) + H2O(l) → Ca(OH)2 (aq) + Heat 1. Quicklime is used for white-washing of walls. 2. The solution of slaked lime is used for whitewashing of walls. 3. CaO reacts slowly with CO2 in air to form a thin layer of CaCO3 on walls. 4. Calcium hydroxide called 'slaked lime' is an inorganic compound. Select the correct answer using the code given below.

CAPF · 2022 · Q39 Relevance score: 2.88

Calcium oxide reacts with water to produce slaked lime. It is an example of

CDS-II · 2014 · Q25 Relevance score: -2.02

When carbon dioxide is passed through lime water, the solution turns milky, but, on prolonged passage, the solution turns clear. This is because