SSC CGL 2022 PYQ — Question 47

The correct answer is Option 1. i.e. CaO.

CaO is the correct chemical formula for quick lime.Calcium oxide, commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline, crystalline solid at room temperature.

• When calcium reacts with water it is called calcium hydroxide. When it is in pure state it is called calcium oxide or Quicklime.

Additional information-

1. CO2 - Carbon dioxide is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature, and as the source of available carbon in the carbon cycle, atmospheric CO₂ is the primary carbon source for life on Earth. 
2. CaCO3 - Calcium Carbonate is the carbonic salt of calcium (CaCO3).makes up almost five percent of the earth's crust and is found all throughout the planet. Calcium carbonate's most common natural forms are limestone and marble.

• [e.g. CaCO3(s) → CaO(s) + CO2(g) Decomposition of limestone to calcium oxide (quicklime) and carbon dioxide on heating.]

        3. Ca(OH)2 - Calcium hydroxide is an inorganic compound with the chemical formula Ca(OH)₂.                It is a colorless crystal or white powder and is produced when quicklime is mixed with water.                It has many names including hydrated lime, caustic lime, builders' lime, slaked lime, cal, and                pickling lime. 

           Ca(OH)₂ → Ca²⁺ + 2 OH. At ambient temperature, calcium hydroxide (portlandite) dissolves in             water to produce an alkaline solution with a pH of about 12.5. Calcium hydroxide solutions                   can cause chemical burns.