What is the formula of quicklime?

(a). Ca(OH)2

(b). CaCl2

(c). CaO

(d). CaSO4

The formula for quicklime is (c) CaO. Quicklime, also known as calcium oxide, is a white, caustic, alkaline substance that is produced by heating limestone (calcium carbonate) in a process called calcination. This process drives off carbon dioxide, leaving behind the oxide form of calcium.

Understanding Quicklime

Quicklime is primarily used in various industrial applications, including steelmaking, water treatment, and as a key ingredient in the production of cement. Its chemical properties make it a versatile compound in many chemical reactions.

The Formation of Quicklime

To grasp how quicklime is formed, consider the following reaction:

• When limestone (CaCO3) is heated, it decomposes into quicklime (CaO) and carbon dioxide (CO2):

CaCO3 (s) → CaO (s) + CO2 (g)

This reaction illustrates how the thermal decomposition of calcium carbonate results in the formation of calcium oxide, which is the chemical name for quicklime.

Properties and Uses

Quicklime is known for its high reactivity, especially with water. When it comes into contact with water, it undergoes an exothermic reaction to form calcium hydroxide (slaked lime):

• CaO (s) + H2O (l) → Ca(OH)2 (aq)

This property is significant in construction and various chemical processes, as it can be used to adjust pH levels or as a drying agent.

Distinguishing Quicklime from Other Compounds

To clarify why the other options are not correct:

• Ca(OH)2 is calcium hydroxide, also known as slaked lime, which is produced when quicklime reacts with water.
• CaCl2 is calcium chloride, a salt used for de-icing and as a drying agent, but it is not related to quicklime.
• CaSO4 is calcium sulfate, commonly found in gypsum, and is used in plaster and drywall, but it does not represent quicklime.

In summary, quicklime is identified by the chemical formula CaO, and its unique properties and reactions make it an essential compound in various industries. Understanding its formation and applications can provide valuable insights into its significance in both chemistry and practical uses.