Question

What is the formula of quicklime?
(a). $Ca{ \left( OH \right) }_{ 2 }$
(b). $Ca{ Cl }_{ 2 }$
(c). CaO
(d). $Ca{ SO }_{ 4 }$

Answer 1

- Hint: Quicklime is the base of calcium that does not contain the hydroxyl group. Quicklime reacts with water to form calcium hydroxide. It is a white crystalline solid that is available as a white powder.

Complete step-by-step solution -
Quicklime is chemically known as calcium oxide. So, the formula of quicklime is CaO. Let us know more about quicklime, some of its physical and chemical properties, and its applications.
When calcium oxide is added to water it forms calcium hydroxide. Its chemical formula is $Ca{ \left( OH \right) }_{ 2 }$. Calcium hydroxide acts as an Arrhenius base. An Arrhenius base releases ${ OH }^{ - }$ in aqueous solutions.
$CaO+{ H }_{ 2 }O\longrightarrow Ca{ \left( OH \right) }_{ 2 }\rightleftharpoons { Ca }^{ 2+ }+2{ OH }^{ - }$
Quicklime is caustic i.e. it destroys or damages any substance through a chemical reaction when it comes into contact. It is alkaline i.e. it is a water-soluble base.
Apart from quicklime calcium oxide is also known to us by the following names: unslaked lime, burnt lime, calcia, and unslaked lime.
It can be prepared by the thermal decomposition of calcium carbonate at temperatures above $82{ 5 }^{ \circ }C$. This process is known as lime-burning or chemically it is known as calcination. The chemical equation for this process is given below.
$Ca{ { CO }_{ 3 } }_{ \left( s \right) }\overset { \triangle }{ \underset { >82{ 5 }^{ \circ }C }{ \longrightarrow } } Ca{ O }_{ \left( s \right) }+{ { CO }_{ 2 } }_{ \left( g \right) }\uparrow$
Quicklime is used in various purposes such as whitewashing, production of aerated concrete blocks, calcium aluminium cement, glass, organic chemicals etc.
Therefore, the formula of quicklime is CaO. So, option c is the correct one.

Note: Don’t confuse between quicklime and slaked lime. Quicklime is calcium oxide (CaO) while slaked lime is calcium hydroxide ( $Ca{ \left( OH \right) }_{ 2 }$ ). As shown earlier, slaked lime is formed when quicklime is dissolved in water.