Chemistry: Calcium Oxide
Calcium Oxide
Calcium (Ca)
Calcium (which name originated from the Latin word for lime, calx) does not occur free in nature. It is found mostly as limestone, gypsum and fluorite. It is the key component of rocks and minerals such as aragonite, calcite, chalk, limestone, marble, and travertine.
This element is found in the flora and fauna (bones, muscles, and nerves, different plants) as well as the food we eat (e.g. milk and other dairy product).
Although calcium is the fifth most abundant element in the earth's crust, it is never attained free in nature given that it easily forms compounds by reacting with oxygen and water.
Sir Humphry Davy in 1808 was the first to isolate metallic calcium .He did this through the electrolysis of a mixture of lime (CaO) and mercuric oxide (HgO). Today, metallic calcium is obtained by displacing calcium atoms in lime with atoms of aluminum in hot, low-pressure containers.
The metal is a silvery color and is rather rigid in texture. Chemically it is one of the alkaline earth elements; it readily forms a white covering of nitride in air, reacts with water, burns with a yellow-red flame, forming largely the nitride.
Calcium combines readily with oxygen to form calcium oxide (CaO): 2Ca + O2 2CaO. Calcium also reacts with the halogens, with cold water, with most acids, and with most nonmetals, such as sulfur and phosphorus.
Elemental calcium has few uses, mostly involving an alloy of the element. For instance, an alloy of calcium and cerium is used in flints in cigarette and other kinds of lighters.
By contrast, the compounds of calcium have a myriad number of uses. By far the most important of these compounds is lime (calcium oxide; CaO).
The most important use of lime is in the production of metals. It is used during the manufacture of steel to remove unwanted sand (silicon dioxide; SiO2) present in iron ore: CaO + SiO2 CaSiO3. The calcium silicate (CaSiO3) formed in this reaction is removed as slag.
Lime is also used in toxic waste control. One measure to remove unwanted gases is to pass them through a solution of calcium oxide in the smokestack. The calcium oxide reacts with and removes certain harmful gases, such as sulfur dioxide (SO2): CaO + SO2 CaSo3.
In water treatment plants, Water purification is also another use of lime. Lime combines with water to form calcium hydroxide [Ca(OH)2], also known as slaked lime. Slaked lime is a sticky precipitate that sinks to the bottom of a tank, carrying with it impurities such as suspended particles and disease-causing microorganisms.
Lime is also the starting point from which more than 150 other industrial chemicals are produced. Some examples include:
1) calcium alginate: a thickening agent (used in ice cream and cheese products)
2) calcium arsenate [Ca3(AsO4)2]: an insecticide
3) calcium carbide (CaC2): used to make acetylene gas and in the manufacture of plastics
4) calcium chloride (CaCl2): used for ice removal and dust control on dirt roads, as a conditioner for concrete, and as an additive for canned tomatoes
5) calcium gluconate [Ca(C6H11O7)2]: as additive in vitamin pills
6) calcium hypochlorite [Ca(OCl) 2]: disinfectant, bleaching agent, algaecide, and fungicide
7) calcium permanganate [Ca)MnO4)2]: used in textile production, as a water sterilizing agent, and in dental procedures
8) calcium phosphate [Ca(PO4)2]: as a supplement in animal feed, as a fertilizer, in the production of dough, and in the making of glass
9) calcium phosphide (Ca3P3): used in fireworks, rodenticide, torpedoes, and flares
10) calcium stearate [Ca(C18H35O2)2]: used in to make wax, cements, plastics, cosmetics, water-resistant materials, paints, and as a food additive
11) calcium tungstate (CaWO4): used in luminous paints, fluorescent lights, and x-ray studies in medicine.
| Physical Properties of Calcium |
| Symbol: Ca Atomic Number:20 Atomic Weight:40.078 Group name: Alkaline earth metal Melting Point:1115 K (842°C or 1548°F) Boiling Point:1757 K (1484°C or 2703°F) Density:1.54 grams per cubic centimeter Phase at Room Temperature:Solid Color: silvery white |
Sources
-www.webelements.com
-www.chemicalelements.com
-Chemistry ,the central science
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