A saturated solution of calcium hydroxide in water. When carbon dioxide gas is bubbled through limewater, a 'milky' precipitate of calcium carbonate is formed:
Ca(OH)2(aq)+CO2(g) → CaCO3(s)+H2O(l)
If the carbon dioxide continues to be bubbled through, the calcium carbonate eventually redissolves to form a clear solution of calcium hydrogencarbonate:CaCO3(s)+CO2(g)+H2O(g) → Ca(HCO3)2(aq)
If cold limewater is used the original calcium carbonate precipitated has a calcite structure; hot limewater yields an aragonite structure.
