Calcium oxide, also known as quicklime, is an alkaline substance which has been in use since the medieval age. It is believed that quicklime is one of the oldest chemicals known to the human race. It can also be referred to as burnt lime.
Preparation of calcium oxide
Calcium oxide can be produced by thermal decomposition of materials like limestone or seashells that contain calcium carbonate (CaCO3; mineral calcite) in a lime kiln. The process that is used to prepare burnt lime is known as calcination. It is a process which starts with thermally decomposing the reactants at high temperatures but ensuring that the temperature is kept well below the melting point.
Calcium carbonate undergoes calcination at temperatures ranging between 1070oC-1270oC. These reactions are usually held in a rotary kiln. The products formed as a result of the reaction are burnt lime and carbon dioxide. The carbon dioxide that is formed is immediately removed so that the reaction is preceded until the completion of the process in accordance with Le-Chatelier’s principle.
CaCO3 → CaO +CO2
This reaction is reversible and exothermic in nature in the forward direction.
Properties of calcium oxide
- Quick lime is an amorphous white solid with a high melting point of 2600o
- It is a very stable compound and withstands high temperatures.
- In the presence of water, it forms slaked lime. This process is called slaking of lime.
CaO+H2O → Ca (OH)2
- It is an oxide which is basic in nature and forms salts when it comes in contact with an acid.
CaO+H2SO4 → CaSO4+H2O
Uses of calcium oxide
- It is extensively used for medicinal purpose and insecticides.
- It finds its application in manufacturing of cement, paper, and high-grade steel.
- Lime is used as a reagent in laboratories for dehydration, precipitation, etc.
- It is the cheapest alkali available which is an important ingredient in the manufacturing of caustic soda.
There are few things that users should keep in mind regarding Calcium Oxides. The reaction between quicklime and water is usually vigorous. Quicklime can cause severe irritation especially when inhaled or if it comes in contact with wet skin or eyes. Some of the effects of inhalation include sneezing, coughing, or labored breathing. Additionally it can also result in abdominal pain, nausea, burns with perforation of the nasal septum, and vomiting. When quicklime reacts with water it can release enough heat to even ignite combustible materials.
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