Calcium carbonate, also referred to as Calcium trioxocarbonate (CaCO3), is one of the most widely available chemical compounds on the earth. It occurs naturally in the earth crust, and is said to make up approximately 7 percent of the earth’s crust (Calcium Carbonate, 2006). The compound goes by different common names such as calcite, limestone, chalk, pearl, marble, aragonite, etc. Naturally, calcium carbonate can be found in almost all rocks. It can also be found in the hard shells of some organisms such as pearls, snails, and eggshells.
Calcium carbonate occurs in two forms with different geometric structural arrangements of the constituent elements (calcium, carbon, and oxygen). The two crystalline forms are calcite and aragonite. Calcium carbonate, when extracted in a pure form exists as a white powder which has a specific gravity of 2.71 (calcite) or 2.93 (aragonite) (Calcium Carbonate, 2006).
Calcium carbonate does not dissolve easily in water. It is poorly soluble in pure water. It has a relative molecular mass of 100g/mol. The bond type between the two major ions: calcium ion (Ca2+) and carbonate ion (CO32-) is the electrovalent type. It has the following chemical properties: reaction with acids to liberate carbon dioxide and water, reaction with water and carbon dioxide to form carbon bicarbonate, and production of calcium oxide and carbon dioxide when heated to temperatures above 900oC.
Calcium carbonate is a very important compound because it is has numerous natural, health and industrial uses. It is used in medicine as a form of therapy in peptic ulcer diseases. It is used as an antacid as a result of its property of reacting with acids in the stomach, liberating carbon dioxide and water. It is also used in construction industries as building materials. In particular, it is used to make cement or mortar which is used to hold blocks together. Again, calcium carbonate is used in the steel manufacturing companies. It is used specifically to absorb any impurity in the molten steel material. Another use of this compound is in the manufacture of papers and glass.
There are different methods of preparation of calcium carbonate. The method which is being investigated in this experiment is one of the most common methods of preparation of the compound. Large amounts of calcium carbonate (especially for industrial uses) are prepared by mining and quarrying. Small amounts can be produced in the laboratory, or can be extracted from a pure mined source. In the laboratory, it is produced by reacting calcium oxide or quicklime (CaO) with water (H2O). This reaction ends with the production of calcium hydroxide (Ca(OH)2). Carbon dioxide is bubbled through calcium hydroxide solution. The end result of this reaction is calcium carbonate (CaCO3). The reactions are as follows:
CaO + H20 ———- Ca(OH)2
Ca(OH)2 + CO2 ———— CaCO3 + H2O
The significance of this investigation is to examine the possibility of preparing calcium carbonate with the above method.
The aim of this experiment is to learn about the preparation of calcium carbonate. This experiment attempts to verify the hypothesis that the above stated method can be used to prepare calcium carbonate.