Chemistry

In chemistry, limewater can be used to detect the presence of carbon dioxide because limewater reacts with carbon dioxide to produce a precipitate of calcium carbonate:

Ca(OH)_{2 (aq)} + CO_{2 (g)} → CaCO_{3 (s)} + H₂O _(l)

If excess CO₂ is added, the following reaction takes place: CaCO₃ + H₂O + CO₂ --> Ca(HCO₃)₂ (colourless)

Limewater is also used in experiments involving aerobic or anaerobic respiration, to determine whether carbon dioxide was produced, by first boiling the limewater and then pouring the solute into the boiling limewater. When limewater reacts with CO₂ it becomes milky, because of the calcium carbonate, or chalk, produced.