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salt11 Lime milk, lime water, lime water reaction

Lime water you have used as an indicator for carbon dioxide in exhaled air.
In the previous experiment you could prove that lime mortar reacts with carbon dioxide of air during setting.
* Left: Heat is produced while quicklime reacts with water to form a powder of slaked lime [Ca(OH)2].
* Photo 2: Lime milk is turbid mixture of calcium hydroxide and water.
* Photo 3: Lime water  is made from lime water by sedimentation and pouring off the clear solution of calcium hydroxide.
* Right: Transfer 2 ml of lime water into two Liquemin bottles, add 1 drop of universal indicator solution to each of them.
  Exhale air into one of the bottles until the colour of the U.I. changes.
Observation and Explanation Right:

The calcium hydroxide dissolved in water reacted with the carbon dioxide like during setting of mortar:       Ca(OH)2 (aq) + CO2----> CaCO3 (s) + H2O
1. The colour change of U.I. from blue to yellow shows that the hydroxide ions of the alkaline solution were consumed.    2. The white sediment is limestone (calcium carbonate).

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