Chemical oxygen formulas with calcium. Calcium properties and application
Calcium history
Calcium was opened in 1808 Hamphrey Davy, which by the electrolysis of haremen and mercury oxide received the Amalgam calcium, as a result of the mercury distillation process from which the metal remained, called calcium. On Latini limesounds like calx, It is this name that was chosen by an English chemist for an open substance.
Calcium is an element of the main subgroup II of the IV periodic period of the periodic system chemical elements DI. Mendeleeva, has atomic number 20 and the atomic mass of 40.08. The adopted designation is Ca (from Latin - Calcium).
Physical and chemical properties
Calcium is a chemically active soft alkaline metal white color. Due to interaction with oxygen and carbon dioxide The surface of the metal fills, so calcium needs a special storage mode - mandatoryly closed container, in which the metal is poured with a layer of liquid paraffin or kerosene.
Calcium - the most famous of the necessary microelements, the daily need for it is from 700 to 1500 mg for a healthy adult, but it increases during pregnancy and lactation, it must be taken into account and receive calcium in the form of drugs.
Finding in nature
Calcium has very high chemical activity, so it is not found in the free (clean) form in nature. Nevertheless, is the fifth in the prevalence in earth Kore, in the form of connections is in sedimentary (limestone, chalk) and mountain breedsah (granite), a lot of calcium contains field spat of anomy.
In living organisms, it is distributed quite widely, its presence is found in plants, animal and human organisms, where it is present, mainly in the composition of teeth and bone tissue.
Calcium digestibility
An obstacle to the normal assimilation of calcium from food is the use of carbohydrates in the form of sweets and alkalis, which neutralize hydrochloric acid The stomach needed to dissolve calcium. The process of learning calcium is quite complicated, so sometimes it is not enough to receive it only with food, an additional receipt of the trace element is necessary.
Interaction with others
To improve the absorption of calcium in the intestine, which has a property to facilitate the process of calcium absorption. When calcium admit (in the form of additives) during the food process, the absorption is blocked, but the reception of calcium preparations separately from food does not affect this process.
Almost all calcium organism (from 1 to 1.5 kg) is in the bones and teeth. Calcium participates in the processes of excitability of the nervous tissue, the reduction of muscles, blood coagulation processes, is included in the kernel and membranes of cells, cellular and tissue liquids, has an anti-allergic and anti-inflammatory effect, prevents acidosis, activates a number of enzymes and hormones. Calcium also participates in permeability regulation cell membranesThe opposite has an action.
Signs of calcium shortage
Signs of calcium shortage in the body are such, at first glance, not related symptoms:
- nervousness, worsening mood;
- heart palpitations;
- cramps, numbness numbers;
- slowdown in growth and children;
- increased blood pressure;
- bundle and fragility of nails;
- pain in the joints, lowering the "painful threshold";
- abundant menstruation.
Causes of calcium shortage
The causes of the lack of calcium are unbalanced diets (especially starvation), low calcium content in food, smoking and passing coffee and caffean-containing drinks, dysbacteriosis, kidney disease, thyroid gland, pregnancy, lactation periods and menopause.
Excess calcium, which may occur with excessive use of dairy products or uncontrolled reception of drugs, is characterized by a strong thirst, nausea, vomiting, loss of appetite, weakness and reinforced urination.
Calcium use in life
Calcium found the use of uranium in the metal rotation of uranium, in the form of natural compounds is used as raw materials for the production of plaster and cement, as a means of disinfection (well-known chlork).
Definition
Calcium - Twentieth element of the periodic table. Designation - CA from Latin "Calcium". Located in the fourth period, IIA group. Refers to metals. The kernel charge is 20.
Calcium belongs to the number of the most common elements in nature. In the earth's crust it contains approximately 3% (mass.). It occurs in the form of numerous deposits of limestone and chalk, as well as marble, which are natural varieties of calcium carbonate Caco 3. Caso 4 × 2H 2 O gypsum is also found in large quantities, Ca 3 phosphorite (PO 4) 2 and, finally, various calcium-containing silicates.
In the form of a simple substance, calcium is a dusting, rather solid metal of white (Fig. 1). The air is quickly covered with a layer of oxide, and when heated heats up a bright reddish flame. With cold water calcium reacts relatively slowly, but hydrogen quickly displaces from hot water, forming hydroxide.
Fig. 1. Calcium. Appearance.
Atomic and molecular weight of calcium
Relative molecular weight of the substance (M R) is a number indicating how many times the mass of this molecule is greater than 1/12 mass of carbon atom, and relative atomic mass An element (A R) - how many times the average mass of the atoms of the chemical element is greater than 1/12 mass of the carbon atom.
Since in the free state of calcium exists in the form of single-name Ca molecules, the values \u200b\u200bof its atomic and molecular weight match up. They are equal to 40.078.
Calcium isotopes
It is known that in the nature of calcium may be in the form of four stable isotopes 40 Ca, 42 Ca, 43 Ca, 44 Ca, 46 Ca and 48 Ca, with an explicit predominance of the isotope 40 Ca (99.97%). Their mass numbers are equal to 40, 42, 43, 44, 46 and 48, respectively. The core of the calcium isotope atom 40 Ca contains twenty protons and twenty neutrons, and the remaining isotopes differ from it only by the number of neutrons.
There are artificial calcium isotopes with mass numbers from 34 to 57s, among which the most stable is 41 CA with a half-life equal to 102 thousand years.
Calcium ions
At the external energy level, the calcium atom has two electrons that are valence:
1S 2 2S 2 2P 6 3S 2 3P 6 4S 2.
As a result of chemical interaction, calcium gives its valence electrons, i.e. It is their donor, and turns into a positively charged ion:
CA 0 -2E → CA 2+.
Molecule and calcium atom
In the free state of calcium exists in the form of single-name molecules Ca. We present some properties characterizing an atom and calcium molecule:
Calcium alloys
Calcium serves as a alloying component of some lead alloys.
Examples of solving problems
Example 1.
| The task | Write the reaction equations with which the following transformations can be carried out: Ca → Ca (OH) 2 → Caco 3 → Ca (HCO 3) 2. |
| Answer | With calcium soluble in water, you can get a muddy solution of the connection known as "Lime Milk" - calcium hydroxide: CA + 2H 2 O → Ca (OH) 2 + H 2. By passing carbon dioxide through a solution of calcium hydroxide solution. Calcium carbonate: 2CA (OH) 2 + CO 2 → Caco 3 + H 2 O. By adding water calcium carbonate and continuing to pass carbon dioxide through this mixture, we obtain calcium bicarbonate: Caco 3 + H 2 O + CO 2 → CA (HCO 3) 2. |
Calcium - element of the 4th period and pa-group of the periodic system, sequence number 20. Electronic formula of an atom [18 AR] 4S 2, oxidation degrees +2 and 0. refers to alkaline earth metals. It has low electronegility (1.04), manifests metallic (main) properties. Forms (as cation) numerous salts and binary compounds. Many calcium salts are small in water. In nature - sixth By chemical prevalence, an element (third among metals) is in the associated form. A vital element for all organisms. Calcium appointments in the soil is replenished with the introduction of lime fertilizers (CAC0 3, CAO, CACN 2 calcium cyanamide, etc.). Calcium, calcium cation and its compounds color the flame of the gas burner into dark orange color ( quality detection).
Calcium Sa.
Silvery and white metal, soft, plastic. In the humid air, fill in the wet air and covered with a film from CAO and CA (OH) 2. There is a reactive; flammable when heated in air, reacts with hydrogen, chlorine, gray and graphite:
Restores other metals from their oxides (industrially important method - calcitermia):
Obtaining Calcium B. Industry:
Calcium is used to remove non-metallic impurities from metal alloys, as a component of lungs and antifriction alloys, to highlight rare metals from their oxides.
Calcium Oxide SAO
Basic oxide. Technical name Negashing lime. White, very hygroscopic. It has an ionic structure of Ca 2+ O 2-. Refractory, thermally stable, volatile when calcining. It absorbs moisture and carbon dioxide from the air. Reacts vigorously with water (with high exo-effect), forms a strong alkaline solution (a hydroxide precipitate is possible), the process is called lime quenching. Reacts with acids, oxides of metals and non-metals. It is used for the synthesis of other calcium compounds, in the production of Ca (O) 2, CAC 2 and mineral fertilizers, like flux in metallurgy, catalyst in organic synthesis, component of binding materials in construction.
Equations of the most important reactions:
Obtaining SAO in industry - Limestone firing (900-1200 ° C):
SASO3 \u003d CAO + CO2
Calcium hydroxide (it) 2
Basic hydroxide. Technical name Gashenny Lime. White, hygroscopic. It has an ionic structure of CA 2+ (it -) 2. Decomposes with moderate heating. It absorbs moisture and carbon dioxide from the air. Multulatory B. cold water (an alkaline solution is formed), even less - in boiling water. A clear solution (lime water) quickly matures due to the fallout of the hydroxide precipitate (the suspension is called lime milk). Quality reaction On ion Ca 2+ - passage of carbon dioxide through lime water with the advent of the CAC0 3 sediment and the transition to the solution. Reacts with acids and acid oxides, joins ion exchange. It is used in the production of glass, lecherous lime, lime mineral fertilizers, for caustification of soda and softening fresh water, as well as for the preparation of lime-based mortars - tough mixtures (sand + exhaust lime + water), which serve as a binder for stone and brickwork, finishing (plastering) of walls and other construction purposes. Held ("setting") of such solutions is due to the absorption of carbon dioxide from the air.
(first electron)
History and origin of the name
The name of the element comes from the lat. Calx (in the Parentine calcis) - "Lime", "soft stone". It was proposed by the English chemist of Davy Gemphri, in 1808. allocated metal calcium with electrolytic method. DEVI subjected the electrolysis mixture of wet gasheny lime with on a platinum plate, which was an anode. The cathode served as a platinum wire, immersed in liquid. As a result of electrolysis, calcium amalgam was obtained. Heat out from her mercury, Davy got a metal called Calcium.
Isotopes
Calcium is found in nature in the form of a mixture of six isotopes: 40 CA, 42 CA, 43 CA, 44 CA, 46 CA and 48 CA, among which the most common - 40 CA is 96.97%. Calcium cores contain a magic number of protons: Z. \u003d 20. Isotopes 40
20 CA20.
and 48
20 CA28.
There are two of the five in nature in nature twice magic nuclei.
Of the six natural isotopes of calcium, five are stable. The sixth isotope 48 Ca, the greatest of six and very rare (its isotopic prevalence is only 0.187%), is experiencing a double beta decay with a half-life (4.39 ± 0.58) ⋅10 19 years.
In rocks and minerals
Calcium, vigorously migrating in the earth's crust and accumulating in various geochemical systems, forms 385 minerals (fourth place by the number of minerals).
Most of the calcium is contained as part of silicates and aluminosilicates of various rocks (granites, gneisses, etc.), especially in the field Plug - Animal CA.
Calcite CaCo 3, CASO 4 Anhydrite, Caso 4 Alabaster Caso 4 · 0.5h 2 O and Caso 4 · 2H 2 O, Fluorite CaF 2, Apatite Ca 5 (PO 4) 3 (F, CA 5 (PO 4) 3 (F, CL, OH), dolomite MGCO 3 · Caco 3. The presence of calcium and magnesium salts in natural water is determined by its rigidity.
A sedimentary breed consisting mainly of hikingrystalline calcite - limestone (one of its varieties - chalk). Under the action of regional metamorphism, limestone is transformed into marble.
Migration in the earth's crust
In the natural migration of calcium, a "carbonate equilibrium" plays a significant role associated with a reversible reaction of the interaction of calcium carbonate with water and carbon dioxide to form a soluble hydrocarbonate:
C A CO 3 + H 2 O + CO 2 ⇄ C A (HCO 3) 2 ⇄ C A 2 + + 2 HCO 3 - (\\ DisplayStyle (\\ Mathsf (Caco_ (3) + H_ (2) O + CO_ (2 ) \\ rightleftarrows Ca (HCO_ (3)) _ (2) \\ rightleftarrows Ca ^ (2 +) + 2HCO_ (3) ^ (-))))(Equilibrium is shifted to the left or right depending on the concentration of carbon dioxide).
Biogenic migration plays a huge role.
In the biosphere
Calcium compounds are almost in all animal and vegetable tissues (see below). A significant amount of calcium is included in living organisms. Thus, hydroxyapatite Ca 5 (PO 4) 3 OH, or, in another record, 3CA 3 (PO 4) 2 · Ca (OH) 2 is the base of the bone vertebral tissue, including a person; Caco 3 calcium carbonate consists of sinks and shells of many invertebrates, egg shell, etc. in alive fabrics of man and animals 1.4-2% Ca (by mass fraction); In the human body weighing 70 kg calcium content - about 1.7 kg (mainly in the composition of the intercellular substance of bone tissue).
Obtaining
Free metal calcium is obtained by the electrolysis of the melt consisting of CaCl 2 (75-80%) and KCl or from CaCl 2 and CAF 2, as well as aluminothermic recovery of Cao at 1170-1200 ° C 4 C A O + 2 A L → C A A L 2 O 4 + 3 C A (\\ DisplayStyle (\\ Mathsf (4CAO + 2AL \\ RIGHTARROW CAAL_ (2) O_ (4) + 3CA)))
Physical properties
Calcium metal exists in two allotropic modifications. Up to 443 ° C stable α -CA with cubic grazenarized grille (parameter but \u003d 0.558 nm), above stable β -CA. with cubic volume-centered type grid α -fe (parameter a. \u003d 0.448 nm). Standard enthalpy Δ H 0 (\\ DisplayStyle \\ Delta H ^ (0)) Transition α → β This is 0.93 kJ / mol.
With a gradual increase in pressure, it begins to show the properties of a semiconductor, but does not become a semiconductor in the full sense of the word (metal is also not). With a further increase in pressure returns to the metallic state and begins to show superconducting properties (the temperature of superconductivity is six times higher than that of mercury, and far exceeds the conductivity all other elements). The unique behavior of calcium seems to be largely on strontium (that is, parallels are preserved in the periodic system).
Chemical properties
In the number of standard calcium potentials is located to the left of hydrogen. Standard electrode potential CA 2+ / CA 0.84 V pair, so calcium actively reacts with water, but without ignition:
C a + 2 H 2 O → C A (O H) 2 + H 2. (\\ displayStyle (\\ Mathsf (Ca + 2H_ (2) O \\ Rightarrow Ca (OH) _ (2) + H_ (2) \\ Uparrow.)))The presence of a dissolved calcium bicarbonate in water largely determines the time rigidity of water. It is called it because, when boiling water, the bicarbonate is decomposed, and Saci 3 falls into the precipitate. This phenomenon leads, for example, to the fact that in the teapot, scale is formed.
Application
The main use of metal calcium is the use of it as a reducing agent when producing metals, especially nickel, copper and stainless steel. Calcium and its hydride are also used to obtain hardly recoverable metals, such as chrome, thorium and uranium. Calcium alloys with lead are used in some types of batteries and in the production of bearings. Calcium granules are also used to remove traces of air from electrovacuum instruments. Pure metallic calcium is widely used in metalothermia when obtaining rare-earth elements.
Calcium is widely used in metallurgy for deoxidation steel along with aluminum or combined with it. Essay treatment with calcium-containing wires occupies the leading position due to the multi-meter calcium effect on the physicochemical state of the melt, macro and microstructure of the metal, the quality and properties of metal products and is an integral part of the steel production technology. In modern metallurgy for entering the calcium melt, an injection wire is used, which represents calcium (sometimes silicocalcations or aluminocalities) as a powder or extruded metal in a steel shell. Along with the deoxidation (removal of oxygen dissolved in steel), the use of calcium allows us to be obtained by nature, the composition and form of non-metallic inclusions that are not destroyed in the course of further technological operations.
Isotope 48 CA is one of the efficient and consumable materials for the production of superhane elements and the opening of new elements of the Mendeleev table. This is due to the fact that calcium-48 is twice the magic core, so its stability allows it to be sufficiently neutron enhancement for the light kernel; In the synthesis of superheassed nuclei, excess neutrons are needed.
Biological role
Calcium concentration in the blood due to its importance for big number vital processes are precisely regulated, and proper nutrition And sufficient consumption of low-fat dairy products and vitamin D deficiency does not occur. The long-term deficiency of calcium and / or vitamin D in the diet leads to an increase in the risk of osteoporosis, and rickets causes in infancy.
Notes
- Grainll solidity 200-300 MPa
- Michael E. Wieser, Norman Holden, Tyler B. Coplen, John K. Böhlke, Michael Berglund, Willi A. Brand, Paul de Bièvre, Manfred Gröning, Robert D. Loss, Juris Meija, Takafumi HiTa, Thomas Prohaska, Ronny Schoenberg, Glenda O'Connor, Thomas Walczyk, Shige Yoneda, Xiang-Kun Zhu. Atomic Weights of the Elements 2011 (IUPAC Technical Report) (English) // Pure and AppLied Chemistry. - 2013. - Vol. 85, no. five . - P. 1047-1078. - DOI: 10.1351 / PAC-REP-13-03-02.
- Red college.: Knunyantz I. L. (ch. Ed.). Chemical encyclopedia: in 5 tons - Moscow: Soviet Encyclopedia, 1990. - T. 2. - P. 293. - 671 p. - 100,000 copies.
- Riley J.p. And Skirrow G. Chemical Oceanography V. 1, 1965.
- PRITYCHENKO B. Systematics of Evaluated Half-Livetes of Double-Beta Decay // Nuclear Data Sheets. - 2014. - June (vol. 120). - P. 102-105. - ISSN 0090-3752. - DOI: 10.1016 / J.NDS.2014.07.018. [Fix]
- PRITYCHENKO B. List of Adopted Double Beta (ββ) Decay Values (Neopr.) . National Nuclear Data Center, Brookhaven National Laboratory. Checked December 6, 2015.
- Handbook of Chemist / Roll.: Nikolsky B. P. et al. - 2nd ed., Un. - M.-L.: Chemistry, 1966. - T. 1. - 1072 p.
- Newspaper. RU: Pressure elements
- Calcium // Big Soviet Encyclopedia: [at 30 tons] / ch. ed. A. M. Prokhorov. - 3rd ed. - M.: Soviet Encyclopedia, 1969-1978.
- Dkkin D. A., Kisilenko V. V. The influence of various factors for the absorption of calcium from the powder wire with a complex filler SC40 (RUS.) // Electrometallurgy: Magazine. - 2009. - May (No. 5). - P. 2-6.
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- Shell Model Of Nucleus
- Institute of Medicine (US) COMMITTEE TO REVIEW DIETARY REFERENCE INTAKES FOR VITAMIN D AND CALCIUM; ROSS AC, TAYLOR CL, YAKTINE AL, DEL VALLE HB, EDITORS (2011).
Calcium - the chemical element II group with atomic number 20 in the periodic system is denoted by the CA symbol (lat. Calcium). Calcium is a soft alkaline-ground metal silver gray.
20 The element element of the Mendeleeevalization of the element comes from the lat. CALX (in the Parental Calcis Padder) - "Lime", "Soft Stone". It was proposed by the English chemist Humphrey Davy, in 1808 allocated metal calcium.
Calcium compounds - limestone, marble, plaster (as well as lime - limestone firing product) were used in the construction case for several thousand years ago.
Calcium is one of the most common elements on Earth. Calcium compounds are in almost all animal and vegetable tissues. It accounts for 3.38% of the mass of the earth's crust (5th place in prevalence after oxygen, silicon, aluminum and iron).
Finding calcium in nature
Due to the high chemical activity of calcium in free form in nature, it is not found.
Calcium accounts for 3.38% of the mass of the earth's crust (5th place in prevalence after oxygen, silicon, aluminum and iron). The content of the element B. sea water - 400 mg / l.
Isotopes
Calcium is found in nature in the form of a mixture of six isotopes: 40CA, 42CA, 43CA, 44CA, 46CA and 48CA, among which the most common - 40CA is 96.97%. Calcium kernels contain the magic number of protons: z \u003d 20. Isotopes
40
20
CA20 I.
48
20
CA28 are two of the five nuclear nuclei with twice magic number.
Of the six natural isotopes of calcium, five are stable. The sixth isotope 48ca, the heaviest of six and very rare (its isotopic prevalence is only 0.187%), is experiencing a double beta decay with a half-life of 1.6 · 1017 years.
In rocks and minerals
Most of the calcium is contained as part of silicates and aluminosilicates of various rocks (granites, gneisses, etc.), especially in the field Plug - Animal CA.
In the form of sedimentary solids, calcium is represented by chalk and limestones consisting mainly of calcite mineral (Caco3). Crystalline form of calcite - marble - occurs in nature much less often.
Calcite CaCO3, Caso4 Anhydrite, Caso4 Alabaster · 0.5H2O and Caso4 Gyps 2H2O, Fluorite CAF2, CA5 Apatites (PO4) 3 (F, CL, OH), Dolomite MGCO3 · Ca5 (PO4) 3 (F, CL, OH), Dolomite MGCO3 · Caco3 is quite widespread. The presence of calcium and magnesium salts in natural water is determined by its rigidity.
Calcium, vigorously migrating in the earth's crust and accumulating in various geochemical systems, forms 385 minerals (fourth place by the number of minerals).
Calcium biological role
Calcium is a common macro-element in the body of plants, animals and humans. In the body of a person and other vertebrates most of its part is in the skeleton and teeth. In the bones of calcium is contained in the form of hydroxyapatitis. Of the various forms of calcium carbonate (lime) consist of "skeletons" of most groups of invertebrates (sponges, coral polyps, mollusks, etc.). Calcium ions are involved in blood clotting processes, and also serve as one of the universal secondary intermediaries inside the cells and regulate a variety of intracellular processes - muscle contraction, exocytosis, including the secretion of hormones and neurotransmitters. The concentration of calcium in the cytoplasm of human cells is about 10-4 mmol / l, in the intercellular fluids of about 2.5 mmol / l.
The need for calcium depends on age. For adults aged 19-50 years and children of 4-8 years, inclusive daily need (RDA) is 1000 mg (contained about 790 ml of fatty milk 1%), and for children aged 9 to 18 years inclusive - 1300 mg per day (contained about 1030 ml of milk with bidity of 1%). IN adolescence Consumption of sufficient calcium is very important due to the intensive growth of the skeleton. However, according to research in the United States, only 11% of girls and 31% of boys aged 12-19 years old achieve their needs. In a balanced diet, most calcium (about 80%) enters the body of a child with milk products. The remaining calcium falls on cereals (including whole grain bread and buckwheat), legumes, oranges, greens, nuts. In the "dairy" products based on dairy fat (butter, cream, sour cream, ice cream based on cream-based calcium is practically not contained. The larger in the dairy product of dairy fat, the less calcium in it. The absorption of calcium in the intestines occurs in two ways: PERCH (transcellular) and intercellular (paracealyllular). The first mechanism is mediated by the action of the active form of vitamin D (calcitriol) and its intestinal receptors. It plays a major role in small and moderate calcium consumption. For larger content Calcium in the diet The main role is started to play intercellular absorption, which is associated with a large gradient of calcium concentration. Due to the Calusing Mechanism, the calcium is absorbed into more than In the twelfth gum (due to the greatest concentration of receptors in Calcitriolar). Due to the intercellular passive transfer, calcium absorption is most active in all three departures of the small intestine. Calcium suction Paracellularly promotes lactose (milk sugar).
The assimilation of calcium is hampered by some animal fats (including fat cow milk and beef fat, but not fat) and palm oil. Palmitic and stearinovaya and stearinovaya contained in such fats fatty acid It is cleaved when digesting in the intestines and the calcium palmitate and calcium stearate (insoluble soaps) are firmly associated with durability. In the form of this soap with a chair is lost both calcium and fat. This mechanism is responsible for the reduction of calcium absorption, a decrease in bone mineralization and a decrease in the indirect indicators of their strength in infants when using children's mixtures based on palm oil (palm olein). In such children, the formation of calcium soaps in the intestine is associated with a seal of the chair, a decrease in its frequency, as well as more frequent joining and colic.
The concentration of calcium in the blood due to its importance for a large number of vital processes is precisely regulated, and with proper nutrition and sufficient consumption of low-fat dairy products and vitamin D deficiency does not occur. The long-term deficiency of calcium and / or vitamin D in the diet leads to an increase in the risk of osteoporosis, and rickets causes in infancy.
Excessive doses of calcium and vitamin D can cause hypercalcemia. The maximum safe dose for adults aged 19 to 50 years is inclusive of 2500 mg per day (about 340 g of EDAM cheese).
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