Following statements are made in connection with carbon dioxide (C02): 1. C02 is a poisonous gas. 2. C02 is an acidic oxide. 3. C02 turns lime water milky. Which of the statement* given above is/are correct?

Carbon dioxide (CO2) is not considered a poisonous gas in the same way as carbon monoxide; it is a naturally occurring component of the atmosphere and a byproduct of respiration [c5]. While it can cause asphyxiation at very high concentrations by displacing oxygen, it is not inherently toxic. Chemically, CO2 is an acidic oxide because it reacts with water to form carbonic acid and reacts with bases like sodium hydroxide to form salts and water [c2, t1, t9]. A standard laboratory test for CO2 involves passing the gas through lime water (calcium hydroxide solution). The CO2 reacts with the lime water to form an insoluble white precipitate of calcium carbonate (CaCO3), which makes the solution appear milky or cloudy [c1, t2, t7]. Therefore, statements 2 and 3 are correct, while statement 1 is incorrect.

Sources

1. [1] 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
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > 2.1.6 Reaction of a Non-metallic Oxide with Base > p. 22
3. [3] Science , class X (NCERT 2025 ed.) > Chapter 5: Life Processes > Activity 5.4 > p. 87
4. [4] https://www.chm.bris.ac.uk/motm/CO2/CO2h.htm