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Jai Ganesh

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Calcium Hydroxide

Calcium Hydroxide

Gist

Calcium hydroxide is a versatile chemical used for many applications, including as a key component in mortars and plasters for construction, a clarifying agent in water and sewage treatment, a neutralizing agent in agriculture to adjust soil pH, a processing aid in the paper industry, and an ingredient in some food products like masa for tortillas. It's also used to remove hair from animal hides in the tanning process, as a disinfectant, and in various chemical manufacturing processes. 

The most common name for the chemical compound Ca(OH)2 is slaked lime. It is also known by several other names, including hydrated lime, caustic lime, builder's lime, pickling lime, and slack lime. 

Summary

Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula Ca(OH)2. It is a colorless crystal or white powder and is produced when quicklime (calcium oxide) is mixed with water. Annually, approximately 125 million tons of calcium hydroxide are produced worldwide.

Calcium hydroxide has many names including hydrated lime, caustic lime, builders' lime, slaked lime, cal, and pickling lime. Calcium hydroxide is used in many applications, including food preparation, where it has been identified as E number E526. Limewater, also called milk of lime, is the common name for a saturated solution of calcium hydroxide.

Uses

Calcium hydroxide is commonly used to prepare lime mortar.

One significant application of calcium hydroxide is as a flocculant, in water and sewage treatment. It forms a fluffy charged solid that aids in the removal of smaller particles from water, resulting in a clearer product. This application is enabled by the low cost and low toxicity of calcium hydroxide. It is also used in fresh-water treatment for raising the pH of the water so that pipes will not corrode where the base water is acidic, because it is self-regulating and does not raise the pH too much.

Another large application is in the paper industry, where it is an intermediate in the reaction in the production of sodium hydroxide. This conversion is part of the causticizing step in the Kraft process for making pulp. In the causticizing operation, burned lime is added to green liquor, which is a solution primarily of sodium carbonate and sodium sulfate produced by dissolving smelt, which is the molten form of these chemicals from the recovery furnace.

In orchard crops, calcium hydroxide is used as a fungicide. Applications of 'lime water' prevent the development of cankers caused by the fungal pathogen Neonectria galligena. The trees are sprayed when they are dormant in winter to prevent toxic burns from the highly reactive calcium hydroxide. This use is authorised in the European Union and the United Kingdom under Basic Substance regulations.

Calcium hydroxide is used in dentistry, primarily in the specialty of endodontics due to its antibacterial properties and induction of hard-tissue deposition.

Details

Calcium hydroxide (Ca(OH)2) is a soft white powder that is widely used as a raw material in the chemical industry. It forms when calcium oxide is mixed with water. The compound has two hydroxide ions (OH−) for each ion of calcium (Ca2+). The chemical is ionic, with aqueous and electrolytic dissociations both producing calcium ions and hydroxide ions.

Production and uses

Calcium hydroxide is usually produced through the reaction of calcium oxide (CaO) with water (H2O). This reaction is highly exothermic, which means that a great deal of heat is produced.

This reaction occurs when water is added to dry portland cement to make concrete, and the mixture becomes warm, releasing heat. An alternate method of production involves reacting sodium hydroxide with calcium chloride in an aqueous double displacement reaction. In this reaction, sodium chloride also forms.

In the construction industry, calcium hydroxide is a main ingredient in mortar for bricks and stone, plaster, and cement. It is mixed with sand and water to create a pastelike slurry. Once the water evaporates, the sand and calcium hydroxide left behind form a strong adhesive material that holds the bricks or stones together.

Calcium hydroxide is used as a neutralizing chemical, because it reacts with acids to create water and a salt in a double displacement reaction. This neutralization can occur in farm soils to help with plant growth or in waterways to reduce the effects of acid rain. It is also added to foods to prevent the food from becoming too acidic.

Calcium hydroxide is one of many chemicals added to industrial scrubbers that remove nitrogen and sulfur oxides from the exhaust gases that are a byproduct of many industrial processes. Removing these oxides helps to reduce the amount of acid rain that forms due to industrial pollutants.

Calcium hydroxide is also used in the manufacturing of some pesticides, in the production of paints and waterproofing materials, and as an additive to oils and lubricants to improve the ability for these fluids to flow. Calcium hydroxide acts as an accelerant in the production of rubber and plastics. It is also used in the paper industry to treat wood so that converting the wood to pulp is easier. When animal hides that will be tanned to create leather need to be chemically treated to remove hair and fats, a solution of calcium hydroxide is used.

In 1920 calcium hydroxide was first used in root canal fillings. Any exposed dental pulp was treated with calcium hydroxide, and in the mid-20th century capping dental pulp with calcium hydroxide became standard practice.

Chemical and physical properties

Calcium hydroxide is soluble in glycerol and in acids but only slightly soluble in water. A saturated solution of calcium hydroxide, called limewater, reacts with acids to form salts. Calcium hydroxide reacts with carbon dioxide, forming calcium carbonate in the process.

Calcium hydroxide has a molar mass of 74.09 grams per mole. It has a melting point of 580 °C (1,076 °F) and a density of 2.24 grams per cubic centimetre.

If the skin is not properly protected, contact with calcium hydroxide can lead to chemical burns. Long-term exposure can cause lung damage.

Additional Information

Calcium Hydroxide, often known by its common names slaked lime or hydrated lime, is a versatile chemical compound with a wide range of applications. From its critical role in construction and water treatment to its use in the food industry and medical field, Calcium Hydroxide is an unsung hero in many essential processes.

What is Calcium Hydroxide?

Calcium Hydroxide, with the chemical formula Ca(OH)2, is an inorganic compound that is widely utilized in various industries due to its reactive properties. This compound is created through the process of combining calcium oxide (quicklime) with water, resulting in an exothermic reaction that produces calcium hydroxide and heat.

Definition and Chemical Composition

Calcium Hydroxide is defined as a white, powdery substance composed of calcium, hydrogen, and oxygen atoms. Its chemical composition is represented by the formula Ca(OH)₂, indicating that each molecule contains one calcium atom bonded to two hydroxide groups. This structure makes it a strong base, capable of neutralizing acids and participating in various chemical reactions.

Common Names

Calcium Hydroxide is known by several common names, reflecting its different uses and forms:

* Slaked Lime: This name emphasizes the hydration process that converts calcium oxide to calcium hydroxide.
* Hydrated Lime: A term used to denote the water content in the compound.
* Pickling Lime: Refers to its use in the food industry, particularly in the pickling process.
* Builders’ Lime: Commonly used in construction and masonry.

Natural Occurrence

In nature, Calcium Hydroxide is found in its mineral form known as portlandite. However, it is more commonly produced synthetically for industrial and commercial applications. The natural occurrence of calcium hydroxide in portlandite is relatively rare, and it is usually encountered in association with volcanic and metamorphic rocks. This mineral can be found in regions with significant geological activity, where high temperatures and pressures facilitate its formation.

In summary, Calcium Hydroxide is a versatile and essential compound with a straightforward yet powerful chemical composition. Its various names and forms reflect its widespread utility across different sectors, and while it does occur naturally, it is predominantly manufactured to meet the demands of modern industry.

Physical and Chemical Properties

Calcium Hydroxide, Ca(OH)2, possesses a range of physical and chemical properties that make it a valuable substance in various applications. Understanding these properties is essential for effectively utilizing and handling this compound.

Appearance and Physical State

Calcium Hydroxide typically appears as a white, odorless powder or crystalline substance. In its solid state, it can be fine and soft to the touch, or it may form larger crystalline aggregates. When mixed with water, it forms a slurry or a viscous paste, which is often referred to as lime putty.

Solubility and pH

Calcium Hydroxide is sparingly soluble in water. At 20°C, about 1.73 grams of Calcium Hydroxide dissolve in one liter of water, forming a solution known as limewater. This solution is mildly alkaline, with a high pH value typically around 12.4. This high pH indicates that Calcium Hydroxide is a strong base, capable of neutralizing acids effectively.

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