# Question #32ecf

##### 1 Answer
May 11, 2015

Whitewash is made by mixing quicklime, which is another name for calcium oxide, $C a O$, with water.

Calcium oxide is obtained from the thermal decomposition reaction of limestone, which is another name used for calcium carbonate, $C a C {O}_{3}$. When you heat limestone, you convert it to calcium oxide and carbon dioxide.

$C a C {O}_{3 \left(s\right)} \to C a {O}_{\left(s\right)} + C {O}_{2 \left(g\right)}$

When calcium oxide is mixed, or slacked, with water, you get slacked lime, which is calcium hydroxide.

$C a {O}_{\left(s\right)} + {H}_{2} {O}_{\left(l\right)} \to C a {\left(O H\right)}_{2 \left(s\right)}$

Calcium hydroxide is one of the main ingreadients in whitewash, along with chalk, or calcium carbonate, $C a C {O}_{3}$.

Calcium hydroxide is converted into calcium carbonate by a process called carbonation

$C a {\left(O H\right)}_{2 \left(s\right)} + C {O}_{\textrm{2 \left(g\right]}} \to C a C {O}_{\textrm{3 \left(s\right]}} + {H}_{2} {O}_{\left(l\right)}$

So, as a conclusion, whitewash is a solution that cxontains calcium hydroxide (slacked lime) and calcium carbonate (chalk).