What is the preparation of calcium oxide and it properties

The preparation of calcium oxide is an example of a chemical process in which calcium reacts with oxygen to produce calcium oxide and heat. The reaction is exothermic and the heat can be used to boil water or produce electricity as well as various useful chemicals. Calcium oxide is also used in the extraction of other elements such as oil, et cetera.

Properties of calcium oxide

1. Stability

Calcium oxide is a very stable compound as evidenced by the fact that calcium metal and calcium hydroxide are extremely reactive with water but calcium oxide is insoluble in water. This property is essential in the preparation of calcium oxide by heating limestone since the heat released during the formation of the more stable compound is used to boil water.

2. High melting point

The value of 2,750 ℃ for its melting point makes it one of only four pure substances that are liquid at or above room temperature (the others being mercury, gallium and bismuth). This property makes it useful as a refractory material in high-temperature furnaces. The high purity of commercially available calcium oxide (>99.8%) also makes it useful for many specialized applications such as deoxidizing and purging with oxygen sensitive materials.

3. Spark-sensitive

Calcium oxide is very spark-sensitive, reacting explosively with combustible substances, causing them to ignite readily. This property is utilized in the purification of hydrogen, which is produced commercially by the electric arc process or by electrolysis of water (as discussed below). The hydrogen thus purified has a purity of better than 99.5%. Another use was in the early history of photography (see Calcium hydride).

4. UV protective

The absorption and reflection of ultraviolet light makes calcium oxide useful in the manufacture of many glass products. These include safety glass, ultraviolet-absorbing windows and plastic lenses.

5. Specialized applications

In addition to its use as a building material, calcium oxide is used (mostly in the form of calcium silicates) as a drying agent in paints, paper glues and many other technical products. It is also used as a flux in welding and as an additive to accelerate certain chemical reactions (e.g., for synthesis of amylase). Calcium oxide is an important component of the dry ice/acetone mixture which produces dry ice from liquid acetone. This application exploits the exothermic reaction between calcium oxide and acetone, in which calcium oxide reacts with the acetone to produce calcium acetate and CO₂

6. Handling precautions

Calcium oxide dust is a severe respiratory irritant, and the vapors of this compound can be dangerous. Safe handling procedures must be employed. It should be used in a fume hood or other appropriate exhaust system.

Preparation of calcium oxide

1. General procedure

Calcium oxide would be obtained by the reaction of calcium metal with water at high temperature and pressure. The reaction is exothermic, and the conversion of carbon dioxide to calcium carbonate at the same time results in a net increase in the quantity of carbon dioxide (which is liberated as vapor), and an even greater release of heat, heating the limestone while it cools down. This temperature range is called a critical temperature range; if temperatures are lower than this range, no reaction occurs. If temperatures are higher than this range, no product will result; if temperatures fall just outside the critical range, either addition or loss of water will occur.

In a large-scale process, the reaction is carried out in a pressure vessel called an autoclave. The autoclave is made of steel or some other material that is resistant to corrosion by calcium oxide and also resistant to high pressure (usually carbon steel or alloy steels). The process is conducted as follows:

Hydrated lime (called "quicklime"), mined limestone containing a mixture of calcium carbonate and calcium hydroxide, typically contains 75% calcium carbonate. The quicklime is heated in a calciner until it begins to decompose and its water content begins to drop.

The residual carbon dioxide is pumped from the calciner into a calcium oxide "burner" at high pressure (3 bar), where it reacts with the lime to produce calcium oxide. The limestone is cooled off, and the calcium oxide is separated from the now-carbon dioxide rich lime by pouring a mixture of water and sodium chloride into the furnace. The mixture boils, as though it were a dry acid, causing all of the carbon dioxide to be liquefied and absorbed by the water-salt solution. At this point, it can be processed further or reused in other reactions.

In conclusion, preparation of calcium oxide is a process which is essential in today's world. Prepared calcium oxide can be used as an addition to glass, and has many other uses. It's interesting to note that this compound is a very simple yet wonderfully complicated compound.