The compound that is formed is calcium hydroxide.
When limestone is decomposed at a high temperature, calcium oxide is formed as the residue.
[tex]CaCO_3 --- > CaO + CO_2[/tex]
When the calcium oxide residue is treated with water, a calcium hydroxide solution is formed.
[tex]CaO + H_2O -- > Ca(OH)_2[/tex]
More on calcium hydroxide can be found here: https://brainly.com/question/9584549
#SPJ1