What is lime water test for …

Limewater Test - To check for carbon dioxide in your breath. Using lime water is a fun and easy way to test for the presence of carbon dioxide. The exhaled carbon dioxide is used to produce a precipitate of calcium carbonate with the lime water. The most effective way to test for CO2 is to bubble the gas through "limewater", a diluted solution of calcium hydroxide (slaked lime). When you bubble carbon dioxide through the solution, it forms a solid precipitate of calcium carbonate – chalk or limestone. Calcium carbonate is insoluble in water.  Carbon dioxide reacts with calcium hydroxide solution to produce a white precipitate of calcium carbonate. Limewater is a solution of calcium hydroxide. If carbon dioxide is bubbled through limewater, the limewater turns milky or cloudy white.