Calcium oxide is a white crystalline substance. This compound is better known as “quicklime.” Common names for calcium oxide are also "calcium oxide", "boil" and "kirabit".
The formation of this substance is carried out by temperature exposure to limestone - a sedimentary rock of organic or chemogenic origin, which contains calcium carbonate, which decomposes into carbon dioxide and oxide. As a food additive, the compound is known under the designation E529.
Solubility in water is a property of calcium oxide that promotes the formation of calcium hydroxide. The compound also undergoes dissolution in a substance such as glycerol.
Calcium oxide: application
The properties of calcium oxide allow it to be classified as a food additive, used in the production of flour and bakery products. It is believed that this compound improves the taste and quality characteristics of food products. Most often, E529 is found in all kinds of baking powders that are actively used for baking. This food additive acts as an emulsifier, allowing you to obtain homogeneous masses from substances that by their nature do not mix, for example, water and oil.
Calcium oxide is used in large quantities in construction in the manufacture of sand-lime bricks. Some time ago, the substance was used as lime cement - as a result of mixing water and calcium oxide, hydroxide is formed, which, in turn, by absorbing carbon dioxide from the air, hardens and turns into calcium carbonate. Nowadays, when constructing residential buildings, they try not to use lime cement, since the resulting structures absorb and accumulate dampness. Moreover, it is also unacceptable for use in laying stoves, since when exposed to high temperatures, it releases asphyxiating carbon dioxide.
It is also worth noting that quicklime can be used as a base for an inexpensive and readily available refractory material. Fused calcium oxide has some resistance to water, and therefore it can be used as a refractory in cases where the use of other materials is impossible or impractical.
Calcium oxide has also found its application in laboratory practice, where it is used to dry substances that do not react with it. In addition, quicklime is used by the petrochemical industry for the production of various additives and lubricants, by the oil refining industry as a reagent and filler, and by the chemical industry, where it is used to produce calcium stearate.
Ecology is another area in which calcium oxide is actively used. Due to its high level of absorption, this compound is used to neutralize wastewater.
Calcium oxide: harm
As a dietary supplement, calcium oxide is harmless and does not pose a threat to human health.. However, its careless use in pure or concentrated form can have a significant negative impact on a person’s well-being. Getting this substance into the body or onto the skin can be fraught with consequences such as a burn of the esophagus and stomach, redness or glassy swelling of the eyes, chemical burns, etc. There are also frequent cases when the unreasonable use of calcium oxide causes conjunctivitis or dermatitis.
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quicklime(rus. Quicklime; English Quicklime; German Ungelöschter Kalk)- an inorganic binary compound of calcium and oxygen with the composition CaO. Astringent mineral crystalline refractory substance of white color. Melting point 2585°C. Exhibits strong basic properties.
In engineering, calcium oxide is usually called quicklime or burnt lime. The last name comes from the method of its preparation: roasting, or “burning out” limestone. It is obtained by burning limestone, chalk and other carbonate rocks. The process is carried out at low temperatures of decomposition of calcium carbonate.
Distribution in nature
Calcium oxide is one of the most abundant compounds in nature. It is often found in natural carbonates, in parallel with magnesium oxide. The main compounds from which CaO is extracted are calcite, marble, limestone, aragonite, dolomite and many others.
Chemical properties
Calcium oxide reacts very vigorously with water, releasing a significant amount of heat and forming calcium hydroxide:
The reaction of calcium oxide with water is technically called “slaking” of lime, and the reaction product, calcium hydroxide, is called slaked lime.
CaO exhibits strong basic properties: it interacts with acids and acid oxides (in particular, it actively absorbs carbon dioxide from the air), with amphoteric oxides:
Calcium is reduced from its oxide by aluminum and coke:
Receipt
Industrial production
Quicklime (calcium oxide) is obtained by calcining (burning) limestone or chalk. Calcium carbonate begins to decompose at 850°C. The higher the temperature, the faster the schedule goes. But above 1200 ° C, impurities in limestone begin to melt, and this complicates the decomposition process. Therefore, “burning out” limestone is carried out at 1000-1200 ° C.
The “burning out” process is carried out in vertical shaft furnaces lined with refractory bricks on the inside. The charge, that is, a mixture of limestone and coke, is loaded into the furnace through the top opening. Pieces of limestone and coke are made so that their diameter is about 10 cm. Then air and flue gases easily pass through the charge, and the limestone decomposes evenly throughout the mass.
Hot gases arising from the combustion of fuel and limestone, rising upward, are gradually cooled, heating the charge. The burnt lime is lowered into the lower part of the kiln, where it is cooled by air supplied from below.
Obtained in the laboratory
The synthesis of calcium oxide can be carried out by burning calcium metal or its hydride:
Another option is the thermal decomposition of calcium oxygen compounds:
Application
Lime is very widely used in construction, as well as in the chemical industry to produce bleach. The annual world production of lime amounts to hundreds of millions of tons.
Slaked lime, that is, calcium hydroxide, is used in construction. For this purpose, quicklime is treated with water. In this case, porous pieces of calcium oxide (quicklime) greedily absorb water and react with it, releasing a significant amount of heat. As a result, part of the water evaporates, and calcium oxide turns into a loose mass of calcium hydroxide (slaked lime), which is called fluffy. When there is excess water, slaked lime forms in the form of a dough-like mass.
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Oxides are complex substances consisting of two elements, one of which is oxygen. Oxides can be salt-forming and non-salt-forming: one type of salt-forming oxides is basic oxides. How do they differ from other species, and what are their chemical properties?
Salt-forming oxides are divided into basic, acidic and amphoteric oxides. If basic oxides correspond to bases, then acidic oxides correspond to acids, and amphoteric oxides correspond to amphoteric formations. Amphoteric oxides are those compounds that, depending on conditions, can exhibit either basic or acidic properties.
Rice. 1. Classification of oxides.
The physical properties of oxides are very diverse. They can be either gases (CO 2), solids (Fe 2 O 3) or liquid substances (H 2 O).
However, most basic oxides are solids of various colors.
oxides in which elements exhibit their highest activity are called higher oxides. The order of increase in the acidic properties of higher oxides of the corresponding elements in periods from left to right is explained by a gradual increase in the positive charge of the ions of these elements.
Chemical properties of basic oxides
Basic oxides are the oxides to which bases correspond. For example, the basic oxides K 2 O, CaO correspond to the bases KOH, Ca(OH) 2.
Rice. 2. Basic oxides and their corresponding bases.
Basic oxides are formed by typical metals, as well as metals of variable valence in the lowest oxidation state (for example, CaO, FeO), react with acids and acid oxides, forming salts:
CaO (basic oxide) + CO 2 (acid oxide) = CaCO 3 (salt)
FeO (basic oxide)+H 2 SO 4 (acid)=FeSO 4 (salt)+2H 2 O (water)
Basic oxides also react with amphoteric oxides, resulting in the formation of a salt, for example:
Only oxides of alkali and alkaline earth metals react with water:
BaO (basic oxide)+H 2 O (water)=Ba(OH) 2 (alkali earth metal base)
Many basic oxides tend to be reduced to substances consisting of atoms of one chemical element:
3CuO+2NH 3 =3Cu+3H 2 O+N 2
When heated, only oxides of mercury and noble metals decompose:
Rice. 3. Mercury oxide.
List of main oxides:
| Oxide name | Chemical formula | Properties |
| Calcium oxide | CaO | quicklime, white crystalline substance |
| Magnesium oxide | MgO | white substance, slightly soluble in water |
| Barium oxide | BaO | colorless crystals with a cubic lattice |
| Copper oxide II | CuO | black substance practically insoluble in water |
| HgO | red or yellow-orange solid | |
| Potassium oxide | K2O | colorless or pale yellow substance |
| Sodium oxide | Na2O | substance consisting of colorless crystals |
| Lithium oxide | Li2O | a substance consisting of colorless crystals that have a cubic lattice structure |
Quicklime is calcium oxide. It is obtained in laboratories and industrially from natural materials. The substance is actively used in construction and industry.
Physical properties
Calcium oxide is an inorganic crystalline substance in the form of a white or gray-white powder, odorless and tasteless. The solid crystallizes into cubic face-centered crystal lattices like sodium chloride (NaCl).
Rice. 1. Cubic face-centered crystal lattices.
A general description of the substance is presented in the table.
Calcium oxide is a caustic substance belonging to the second hazard class. It exhibits aggressive properties when interacting with water, forming slaked lime.
Rice. 2. Calcium oxide powder.
Receipt
Calcium oxide is also called burnt lime due to the method of production. Quicklime is produced by heating and decomposing limestone - calcium carbonate (CaCO 3).
This is a natural substance found in the form of minerals - aragonite, vaterite, calcite. Included in marble, chalk, limestone.
The reaction for producing calcium oxide from limestone is as follows:
CaCO 3 → CaO + CO 2 .
In addition, quicklime can be obtained in two ways:
- from simple substances, building up an oxide layer on the metal -
2Ca + O 2 → 2CaO;
- during heat treatment of calcium hydroxide or salts -
Ca(OH) 2 → CaO + H 2 O; 2Ca(NO3)2 → 2CaO + 4NO2 + O2.
Reactions occur at high temperatures. The combustion temperature of limestone is 900-1200°C. At 200-300°C, oxide begins to form on the metal surface. For the decomposition of salts and hydroxide, a temperature of 500-600°C is required.
Chemical properties
Calcium oxide is a higher oxide and exhibits maximum oxidizing properties. The compounds interact with inorganic substances and free halogens. The main chemical properties of the oxide are given in the table.
Application
The oxide is used in the food industry as:
- flour and bread improver;
- food additive E529;
- acidity regulator;
- yeast nutrient medium;
- catalyst for hydrogenation (addition of hydrogen) of fats.
In addition, quicklime is used in the chemical and construction industries for the production of various substances:
- oils;
- calcium stearate;
- grease;
- fireproof materials;
- gypsum;
- high alumina cement;
- sand-lime brick.
Rice. 3. Cement, brick, gypsum are obtained from calcium oxide.
What have we learned?
Calcium oxide or quicklime is a crystalline substance that reacts violently with water and forms slaked lime. Widely used in industry, in particular food and construction. Registered as food additive E529. It has high melting and boiling points and is soluble only in glycerol. Formed when calcium carbonate is burned. It exhibits oxidizing properties, forms salts with oxides and acids, and interacts with carbon and aluminum.
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Calcium oxide, formula CaO, is often called quicklime. This publication will tell you about the properties, preparation, and use of this substance.
Definition
Calcium oxide is a white crystalline substance. In some sources it may be called calcium oxide, quicklime, “boiler” or kirabit. Quicklime is the most popular trivial name for this substance. It is the only and highest calcium oxide.
Properties
The oxide is a crystalline substance having a cubic face-centered crystal lattice.
It melts at a temperature of 2570 o C and boils at 2850 o C. It is a basic oxide; its dissolution in water leads to the formation of calcium hydroxide. The substance may form salts. To do this, it must be added to an acid or acid oxide.
Receipt
It can be obtained by thermal decomposition of limestone. The reaction goes like this: calcium carbonate is gradually heated, and when the temperature of the environment reaches 900-1000 o C, it decomposes into gaseous tetravalent carbon oxide and the desired substance. Another way to obtain it is through a simple compound reaction. To do this, a small amount of pure calcium is immersed in liquid oxygen, followed by a reaction, the product of which will be the desired oxide. The latter can also be obtained through the decomposition of calcium hydroxide or calcium salts of certain oxygen-containing acids at high temperatures. For example, consider the decomposition of the latter. If you take calcium nitrate (the remainder is taken from nitric acid) and heat it to 500 o C, then the reaction products will be oxygen, nitrogen dioxide and the desired calcium oxide.
Application
This substance is mainly used in the construction industry, where it is used to produce sand-lime brick. Previously, calcium oxide was also used in the manufacture of lime cement, but the latter was soon stopped being used due to the absorption and accumulation of moisture by this compound. And if it is used to lay a stove, then when it is heated, suffocating carbon dioxide will hover in the room. Also, the substance now discussed is known for its resistance to water. Because of this property, calcium oxide is used as a cheap and accessible refractory. This compound is necessary in any laboratory when drying substances that do not react with it. Calcium oxide is known in one industry as the food additive E529. Also, a 15% solution of this substance is needed in order to remove sulfur dioxide from certain gaseous compounds. Calcium oxide is also used to produce “self-heating” dishes. This property is provided by the process of heat release during the reaction of calcium oxide with water.
Conclusion
That's all the basic information about this connection. As mentioned above, it is often called quicklime. Did you know that the concept of lime in chemistry is very flexible? There are also slaked, bleach and soda lime.
