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.

The reaction CaO(s) + H2O(l) → Ca(OH)2(aq) + Heat describes the formation of slaked lime (calcium hydroxide) from quicklime (calcium oxide) [1]. Statement 1 is incorrect because quicklime is the precursor; it is the resulting solution of slaked lime that is used for whitewashing walls (Statement 2) [1]. Statement 3 is incorrect because it is the calcium hydroxide (slaked lime) on the walls, not CaO, that reacts slowly with atmospheric CO2 to form a thin, shiny layer of calcium carbonate (CaCO3) [3]. Statement 4 is correct as calcium hydroxide is a well-known inorganic compound [1]. Therefore, only statements 2 and 4 are accurate. The carbonation process typically takes 2-3 days to develop the characteristic hard, white finish of calcium carbonate [3].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 1: Chemical Reactions and Equations > Figure 1.3 > p. 6
2. [3] https://en.wikipedia.org/wiki/Whitewash