Calcium is a reactive alkaline earth metal that when exposed to the air generates a black oxide-nitride coating. Its physical and chemical properties are most similar to those of strontium and barium, its heavier homologues. After iron and aluminium, it is the fifth most abundant element in the Earth’s crust and the third most abundant metal. Calcium carbonate is the most prevalent calcium compound on Earth, and it may be found in limestone and the fossilized remains of early sea life. Other calcium compounds include gypsum, anhydrite, fluorite, and apatite.
Calcium has the chemical symbol Ca and the atomic number 20.
Properties of Calcium are:
- It has a silvery-white metallic finish.
- It has a solid phase.
- It is a fairly soft metal.
- It has a cubic structure.
- It’s ductile and can be beaten into very thin sheets. It has the ability to be pressed, rolled, and cut.
- It can be shaped or bent because it is malleable.
- It has high melting and boiling point
Uses of Calcium
- Calcium’s biological job is to give the skeleton strength and structure. It is necessary for the health of the bones and teeth.
- Calcium ions on bone surfaces interact with those in bodily fluids, allowing ion exchange, which is critical in maintaining calcium balance in the blood and bone.
- Coagulation, nerve signal transmission, hormone signalling, and muscle contraction are just a few of the critical processes that calcium in the blood plays a role.
- Calcium can be used as a reducing agent in the metal extraction process.
- Calcium is also used as an alloying agent in the production of some metals.
- Calcium carbonate is used in the manufacture of cement and mortar, as well as in the glass industry.
Some important Compounds of Calcium
Calcium Oxide
Calcium oxide (CaO), sometimes known as quicklime or burned lime, is an extensively used chemical component. At room temperature, it is a white, caustic, alkaline, crystalline solid. Lime, in its broadest sense, refers to calcium-containing inorganic materials dominated by carbonates, oxides, and hydroxides of calcium, silicon, magnesium, aluminium, and iron. Quicklime is the single chemical compound of calcium oxide. Free lime is calcium oxide that does not react in building materials such as cement during manufacturing.
Properties of CaO are:
- Quick lime is a white amorphous solid with a melting point of 2600°.
- It is a very stable compound that can withstand extreme temperatures.
- Slaked lime is formed in the presence of water. This is referred to as lime slaking.
CaO+H2O → Ca(OH)2
- It is a basic oxide that forms salts when it comes into contact with an acid.
- This compound forms a cubic crystal lattice when crystallized.
- This chemical is known to create a bright glow when heated to temperatures above 2400 degrees Celsius.
Uses of CaO are:
- It is widely used in medicine and as an insecticide.
- It is used in the production of cement, paper, and high-quality steel.
- Lime is used as a reagent in laboratories for dehydration, precipitation processes, and other procedures.
- It is the least expensive alkali available and is used in the production of caustic soda.
- Calcium is necessary for animal life because it is a component of bones, shells, and teeth. The most common calcium compound is calcium carbonate, which is used by potters to make calcium oxide for glazes.
Calcium Hydroxide (Ca(OH)2)
Calcium hydroxide (slaked lime) is a chemical compound with the formula Ca(OH)2. When quicklime (calcium oxide) is mixed or slaked with water, it produces a colourless crystal or white powder. It is also known as hydrated lime, caustic lime, and pickling lime. Calcium hydroxide is used in a wide range of applications, including food preparation. A saturated solution of calcium hydroxide is known as limewater.
Properties of Ca(OH)2 are:
- Its crystal structure is hexagonal. It is not very soluble in water, and its solubility decreases as temperature rises. This compound tends to lose water and decompose at temperatures close to its melting point.
- It is very soluble in glycerol and acids, but only slightly so in water. It forms a solution that behaves as a mild base when dissolved in water to saturation.
- When limewater reacts with acids, it produces salts.
- Metals such as aluminium are also reacted with and dissolved by a saturated solution of calcium hydroxide in water.
- Calcium carbonate is formed when it reacts with carbon dioxide (CaCO3). Carbonatation is the common name for this reaction.
Uses of Ca(OH)2 are:
- Calcium hydroxide is used as a clarifying agent or as a flocculant in the sewage treatment process.
- It is used in the paper industry during the Kraft process, which converts wood into wood pulp.
- It is a critical component in the production of ammonia.
- Calcium hydroxide is used as an ingredient in the production of many plastics.
- This compound is used to fill cavities in human teeth during root canal procedures.
- Carbonation, which involves the use of Ca(OH)2, is used to process sugar beets and sugarcane.
- In the leather industry, calcium hydroxide is used to separate the fur/hair from the animal hide.
Calcium Carbonate (CaCO3)
Calcium carbonate, also known as CaCO3, is a chemical compound with the formula CaCO3. It is the principal component of eggshells, snail shells, seashells, and pearls and can be found in rocks as the minerals calcite and aragonite (most famously as limestone). Calcium carbonate, the active element in agricultural lime, is created when calcium ions in hard water react with carbonate ions to form limescale.
Properties of CaCO3 are:
- It’s a light powder.
- When heated to 1200 degrees Celsius, it decomposes into carbon dioxide.
- It produces carbon dioxide as a byproduct when it reacts with dilute acid.
Uses of CaCO3 are:
- The pulp and paper industry makes extensive use of calcium carbonate. It can be used as a filter and a pigment, allowing for the creation of a whiter, higher-quality pigment than other minerals.
- Calcium carbonate is used in the construction industry as a filler in concrete to increase its durability and appearance, as well as to purify metals for use in construction applications.
- Calcium carbonate is also used in fertilizers to provide calcium to plants and to keep the soil’s pH stable.
- Calcium carbonate can also be used as a food additive for both livestock and humans, as well as a vitamin supplement.
- Calcium carbonate is used in water and sewer treatment plants to remove acidity and impurities.
Sample Questions
Question 1: Is calcium hydroxide acidic or basic?
Answer:
When dissolved in aqueous solutions, calcium hydroxide, also known as slaked lime (Ca(OH)2), is a source of hydroxide ions. As a result, this compound is a base. This compound releases OH– ions as a result of electrolyte dissociation.
Question 2: Name a calcium-rich fruit.
Answer:
Apricot, gooseberry, figs, raisins are the fruits rich in calcium.
Question 3: How do we identify carbonate salt?
Answer:
To determine whether a mineral or rock contains calcium carbonate, strong acids such as hydrochloric acid can be added. Carbon dioxide will be produced if the sample contains calcium carbonate.
Question 4: What are the chemical properties of calcium hydroxide?
Answer:
It is very soluble in glycerol and acids, but only slightly so in water. It forms a solution that behaves as a mild base when dissolved in water to saturation (called limewater).
Question 5: What are the biological uses of calcium?
Answer:
Calcium’s biological job is to give the skeleton strength and structure. It is necessary for the health of the bones and teeth. Calcium ions on bone surfaces interact with those in bodily fluids, allowing ion exchange, which is critical in maintaining calcium balance in the blood and bone.