Which one of the following does not represent the salt, Calcium carbonate?

Calcium carbonate (CaCO3) is a common chemical compound found in various natural forms. Limestone, chalk, and marble are all different physical forms of calcium carbonate [3]. Limestone and chalk are sedimentary rocks primarily composed of the mineral calcite, which is pure calcium carbonate [1]. Marble is a metamorphic rock also composed of calcium carbonate. In contrast, lime water is not calcium carbonate; it is a solution of calcium hydroxide (Ca(OH)2) in water [3]. When carbon dioxide is passed through lime water, a chemical reaction occurs that produces a white precipitate of calcium carbonate, which makes the solution appear milky [2]. Therefore, while lime water can be used to produce calcium carbonate, it does not represent the salt itself in its initial state [3].

Sources

1. [3] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > Activity 2.5 > p. 21
2. [1] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 8: Limestone and Chalk Landforms > Limestone and Chalk > p. 76
3. [2] 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