Carbon and its Compounds

Calcium Carbonate

Calcium carbonate is an active ingredient in the agricultural lime which forms when calcium ions react with the carbonate ions in hard water to form as limescale. It is medically applicable as a calcium supplement or an antacid, but over-consumption can be dangerous and could lead to poor digestion.

Calcium Carbonate

                                                                                           Calcium Carbonate

What is Calcium Carbonate?

Calcium carbonate is the inorganic chemical substance with a chemical formula CaCO3. Calcium carbonate is a chemical compound which, is among the most common chemical compounds first encountered in school classrooms where the chalk usage (a form of CaCO3) is common. It is also present in the crust of the earth.

It can also be present in many other kinds, such as marbles, limestone, etc. Though they are available in different forms, they are chemically identical and differ only physically. Calcium carbonate is a known non-toxic and odourless compound widely found as a white mineral that naturally occurs in limestones, chalks, marbles and pearls.

Calcium Carbonate Formula

  • It is an inorganic chemical substance with a chemical formula of CaCO3.
  • It is a white insoluble powder-like material that occurs naturally in calcites, minerals, limestone, chalk, marble, shells, pearls, and etc.
  • Also, it is useful medicinally as an antacid or a calcium supplement, also sometimes used as a filler in cosmetics. And as a disinfectant agent in swimming pools and as a pH corrector.
  • It is widely applicable in the manufacturing industry as a building material (marble), a quick-lime and a cement ingredient.

Preparation of Calcium Carbonate (CaCO3)

  1. CaCO3 is produced by the use of carbon dioxide and slaked lime as raw materials. When carbon dioxide passes through the slaked lime, it obtains the calcite. Another approach used to produce calcite is the addition of sodium carbonate to calcium chloride.

\(Ca (OH)_2 + CO_2 \rightarrow  CaCO_3 + H_2O \\\\\)

\(CaCl_2 + Na_2CO_3 \rightarrow  CaCO_3 + 2NaCl\)

When the carbon dioxide pass in bulk, it contributes to the production of calcium hydrogen carbonate.

  1. For preparation on a large scale, the process is bypassing the carbon dioxide gas through calcium hydroxide (slaked lime). However, if carbon dioxide becomes excess, it produces a soluble calcium hydrogen carbonate.

\(Ca(OH)_2 + CO_2 \rightarrow CaCO_3 + H_2O\)

Commercial Production of Calcium Carbonate (CaCO3)

Commercial manufacturing of calcium carbonate (CaCO3) is of two kinds. Both classes perform industrially on the basis of the particle size and the characteristics of the product.

Ground Calcium Carbonate: It is produced by the extraction and processing of naturally occurring deposits. The shape of the GCC crystal is irregularly rhombohedral, and its distribution is broader in size.

Precipitated Calcium Carbonate: It is produced by the chemical precipitation process with the help of a carbocation process or a bulk chemical processes by-product. The structure of the PCC crystal is dependent on the product, and the particles are more regular and uniform with a narrow distribution size.

PCC has smaller particles of greater purity and is less abrasive and tends to have a higher brightness than GCC.

Structure of Calcium Carbonate (CaCO3)

The thermodynamically stable structure of CaCO3 is hexagonal \(\beta-CaCO_3\)(the mineral calcite) under normal conditions. Other forms are possible to be made, the denser \(2.83 g/cm^3\) orthorhombic \(\lambda-CaCO_3\) (mineral aragonite) and, hexagonal \(\mu-CaCO_3\), which occur as mineral vaterite. Like, preparation of aragonite form at temperatures above 85°C and preparation of vaterite at 60°C is possible. Calcite contains calcium atoms coordinated with six oxygen atoms, and nine oxygen atoms co-ordinated in aragonite. The composition of the vaterite is not well known.

Magnesium carbonate (MgCO3) has calcite structure, while the strontium carbonate and the barium carbonate (SrCO3 and BaCO3) have an aragonite structure, reflecting their larger ionic radii.

Properties of Calcium Carbonate (CaCO3)

  • Calcium Carbonate is known as fluffy powder.
  • When heated up to 1200K, it decomposes to form carbon dioxide.
  • It produces carbon dioxide as a by-product when it reacts with dilute acid.
  • Calcium carbonate decomposes to form calcium oxide and carbon dioxide at a temperature of 1200 K.
  • Calcium carbonate is formed by carbon dioxide when reacting with dilute acids.
  • The molecular weight of the Calcium Carbonate (CaCO3) is 100.0869 g/mol.
  • The molar mass of CaCO3 is 100.0869 g/mol.

The occurrence of Calcium Carbonate

Geological Sources: Calcite, aragonite and vaterite are pure minerals containing calcium carbonate. Industrially significant source rocks that are primarily calcium carbonate also include limestones, chalks, travertines and marbles. Corals are more common in warm, clean tropical waters than in the polar regions where the waters are cold. Calcium carbonate sources like planktons  (coccoliths and planktic foraminifera), bryozoa, sponges, echinoderms, coral algae, brachiopods, molluscs, are usually found in shallow water regions because of the abundant light and, filterable food.

Biological Sources: Eggshells, snail shells and most seashells are primarily calcium carbonate, which is also a commercial source of this chemical. Recently oyster shells have been recognised as a source of dietary calcium which, are also a practical industrial source. Dark green vegetables, including broccoli and kale, contain large quantities of calcium carbonate on a diet but are not functional as an industrial source.

Uses of Calcium Carbonate

  • It plays a major role in the construction, either as a building material (marble) or as an ingredient in cement.
  • Pharmaceutical industries use it for manufacturing antacids, tablets made of base materials, etc.
  • It is also a calcium supplement source for humans.
  • It plays a role in the manufacturing of paints, paper, plastics, etc.

FAQs about Calcium Carbonate

Q.1. What is the use of calcium carbonate?

Answer. It is medically applicable as a calcium supplement or an antacid to treat stomach upset, heartburn, and acid indigestion. But over-consumption can be dangerous and could lead to poor digestion.

Q.2. List out some calcium-rich daily foods.

Answer. There are several foods which we eat daily contains calcium. Like broccoli, kale, soybeans, figs, oranges, apricots, almond milk, raisins, cereals, tofu, sardines, shrimps, diary products like yoghurt, milk, cheese are few of the examples of calcium-rich daily foods.

Q.3. Is limestone a calcium carbonate?

Answer. Limestone is a sedimentary rock primarily consisting of calcium carbonate (CaCO3), mainly as calcite or aragonite. Limestone has two origins;

  1. Biogenic precipitation from seawater, the reason being lime secreting organisms and foraminifera.
  2. Mechanical transport and deposition of pre-existing limestones, developing clastic deposits. Travertine, tufa, caliche, chalk, sprite and micrite are all different types of limestone.

Q.4. How should one take a calcium carbonate medicine?

Answer. Calcium Carbonate comes as a pill, a chewable tablet, a capsule, and a liquid to drink. One should take the medication three to four times a day. Follow the instructions on your medication or product label closely and ask your doctor or pharmacist to clarify any part you don’t understand. Take your calcium carbonate exactly as instructed.

Chew the chewable tablets carefully before swallowing. Do not swallow them whole. After taking either regular or chewable tablets or pills, drink a full glass of water. Any liquid types of calcium carbonate have to be shaken long before use. Do not use calcium carbonate as an antacid for longer than two weeks until the doctor prescribes it.

Q.5. What are the chemical formula and molar mass of calcium carbonate?

Answer. The chemical formula of calcium carbonate is CaCO3. And its molar mass is 100.0869 g/mol.

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