Question

Which of the reactions represents "slaking of lime" ?

• A. $CaCO _{3} \rightleftharpoons CaO + CO _{2}$
• B. $CaO + CO _{2} \rightarrow CaCO _{3}$
• C. $CaO + H _{2} O \rightarrow Ca ( OH )_{2}$
• D. $CaO + SiO _{2} \rightarrow CaSiO _{3}$

Answer 1

Answer: (C)

The word slaking means the addition of water to calcium oxide powder (lime). The resulting product is calcium hydroxide. (milk of lime)
$CaO + H _{2} O \rightarrow Ca ( OH )_{2}$
The reaction is exothermic, so the mixture heats up. Slaking is a key step in the most widely used procedure for formation of precipitated calcium carbonate.