When solid calcium hydroxide is added to water.?
Calcium hydroxide is not that soluble in water. So when you add hydrochloric acid it mops up the available hydroxide ions. But as more calcium hydroxide dissolves it will revert the solution back to its hydroxide, alkaline state, turning the indicator back to blue. By adding more acid this will continue until all of the calcium hydroxide has been reacted to for calcium chloride. Ca(OH)2 + 2HCl = CaCl2 + 2H2O There is another point to make, when making calcium hydroxide, which is burning calcium carbonate to form calcium oxide and slaked with water to form the hydroxide, not all of the oxide has been reacted. So when water is added there is an excess of hydroxide ions which is something else you may witness.
