Correct Option
The correct option is (c) 1 and 3 only.
Explanation
The lime water test is a standard qualitative analysis method used to detect the presence of carbon dioxide gas. It relies on a precipitation reaction between a base (calcium hydroxide) and a non-metallic oxide (carbon dioxide).
Statement-wise Analysis
- Statement 1 is Correct: The lime water test is the definitive standard test for Carbon Dioxide ($CO_2$). When carbon dioxide is bubbled through lime water, the solution turns cloudy or milky, confirming the presence of the gas.
- Statement 2 is Incorrect: The milky appearance is caused by the formation of Calcium Carbonate ($CaCO_3$), which is an insoluble white precipitate. Calcium Oxide ($CaO$), also known as quicklime, is not formed in this reaction. The reaction is:
$Ca(OH)_2 (aq) + CO_2 (g) \rightarrow CaCO_3 (s) + H_2O (l)$ - Statement 3 is Correct: The chemical name for lime water is Calcium Hydroxide ($Ca(OH)_2$). It is prepared by dissolving slaked lime in water to form a saturated solution.
Key Takeaway
Lime water ($Ca(OH)_2$) turns milky upon contact with Carbon Dioxide due to the formation of insoluble Calcium Carbonate ($CaCO_3$). If excess $CO_2$ is passed, the milkiness disappears due to the formation of soluble Calcium Bicarbonate.