The reaction that occurs on passing carbon dioxide gas through lime water is

When carbon dioxide gas is passed through lime water (an aqueous solution of calcium hydroxide), a chemical reaction occurs that produces calcium carbonate and water [3]. The chemical equation for this process is Ca(OH)2 + CO2 -> CaCO3 + H2O [1]. The formation of calcium carbonate, which is an insoluble white substance, causes the lime water to turn milky or turbid [3]. This reaction is a standard laboratory test for the presence of carbon dioxide [3]. If carbon dioxide continues to be bubbled through the solution in excess, the insoluble calcium carbonate reacts further with the CO2 and water to form calcium hydrogencarbonate (Ca(HCO3)2), which is soluble in water, causing the milkiness to disappear [3]. However, the primary reaction for the initial passing of CO2 through lime water is the formation of the carbonate precipitate [3].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 1: Chemical Reactions and Equations > QUESTIONS > p. 7
2. [3] Science-Class VII . NCERT(Revised ed 2025) > Chapter 5: Changes Around Us: Physical and Chemical > Fig. 5.2: Blowing air in (a) tap water; (b) lime water > p. 61
3. [2] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > Activity 2.5 > p. 21