Essay
in chemistry
Subject : Potassium and sodium.
Completed :
11th grade student
71 schools
Sivakov Nikolay
Saint Petersburg
2001
Content
1. History of potassium and sodium. 32. Sodium and potassium in nature. 5
3. Preparation and use of sodium and potassium. 6
4. Physical properties. Chemical properties. 7
5. Caustic alkalis. 8
6. Sodium and potassium salts. 10
7. List of references 11
From the history of potassium and sodium.
The name "sodium" (English and French: Sodium, German: Natrium) comes from ancient word, common in Egypt, among the ancient Greeks (vixpov) and Romans. It is found in Pliny (Nitron) and other ancient authors and corresponds to the Hebrew neter. IN ancient Egypt natron, or nitron, was generally called an alkali obtained not only from natural soda lakes, but also from plant ash. It was used for washing, making glazes, and mummifying corpses. In the Middle Ages, the name nitron (nitron, natron, nataron), as well as boron (baurach), also applied to saltpeter (Nitrum). Arab alchemists called alkali alkali. With the discovery of gunpowder in Europe, saltpeter (Sal Petrae) began to be strictly distinguished from alkalis, and in the 17th century. already distinguished between non-volatile, or fixed alkalis, and volatile alkali (Alkali volatile). At the same time, a difference was established between vegetable (Alkali fixum vegetabile - potash) and mineral alkali (Alkali fixum minerale - soda). IN late XVIII V. Klaproth introduced the name natron (Natron) for the mineral alkali, or soda, and for the vegetable alkali - potassium (Kali), Lavoisier did not place the alkali in the "Table" simple bodies", indicating in a note to it that this is probably complex substances, which will someday be decomposed. Indeed, in 1807 Davy, by electrolysis of slightly moistened solid alkalis, obtained free metals - potassium and sodium, calling them potassium and sodium. IN next year Gilbert, publisher of the famous Annals of Physics, proposed calling the new metals potassium and sodium (Natronium); Berzelius shortened last name to "sodium" (Natrium). IN early XIX V. in Russia sodium was called sodia (Dvigubsky, 182i; Solovyov, 1824); Strakhov proposed the name sod (1825). Sodium salts were called, for example, soda sulfate, hydrochloric soda, and at the same time acetic soda (Dvigubsky, 1828). Hess, following the example of Berzelius, introduced the name sodium.
Potassium (English Potassium, French Potassium, German Kalium) was discovered in 1807 by Davy, who performed the electrolysis of solid, slightly moistened caustic potassium. Davy called the new metal Potassium, but this name did not stick. Godfather the metal turned out to be Gilbert, the famous publisher of the magazine "Annalen de Physik", who proposed the name "potassium"; it was adopted in Germany and Russia. Both names come from terms that were used long before the discovery of potassium metal. The word potassium is derived from the word potash, which probably appeared in the 16th century. It is found in Van Helmont in the second half of the 17th century. is widely used as the name of a commercial product - potash - in Russia, England and Holland. Translated into Russian, the word potashe means “pot ash or ash boiled in a pot”; in the XVI - XVII centuries. potash was obtained in huge quantities from wood ash, which was boiled in large boilers. Potash was used to prepare mainly liter (purified) saltpeter, which was used to make gunpowder. Especially a lot of potash was produced in Russia, in the forests near Arzamas and Ardatov in mobile factories (Maidans) that belonged to a relative of Tsar Alexei Mikhailovich, a close boyar B.I. Morozov. As for the word potassium, it comes from the Arabic term alkali (alkaline substances). In the Middle Ages, alkalis, or, as they said then, alkaline salts, were almost indistinguishable from each other and were called by names that had same value: natron, borax, varek, etc. The word kali (qila) was found around 850 among Arab writers, then the word Qali (al-Qali) began to be used, which meant a product obtained from the ash of some plants, these words are associated Arabic qiljin or qaljan (ash) and qalaj (to burn). In the era of atrochemistry, alkalis began to be divided into “fixed” and “volatile”. In the 17th century there are names alkali fixum minerale (mineral fixed alkali or sodium hydroxide), alkali fixum. vegetabile (vegetable fixed alkali or potash and caustic potassium), as well as alkali volatile (volatile alkali or NH 3 ). Black established a distinction between caustic and soft, or carbonic, alkalis. Alkalies do not appear in the Table of Simple Bodies, but in a note to the table Lavoisier indicates that fixed alkalis (potash and soda) are probably complex substances, although their nature components has not yet been studied. In Russian chemical literature of the first quarter of the 19th century. potassium was called potassium (Soloviev, 1824), potash (Strakhovy, 1825), potash (Shcheglov, 1830); in the "Dvigubsky Store" already in 1828, along with the name potash (potash sulfate), the name potassium (caustic potassium, salt potassium, etc.) is found. The name potassium became generally accepted after the publication of Hess's textbook.
Sodium and potassium.
Alkali metals are not found in free form in nature. Sodium and potassium are found in various compounds. The most important is the compound of sodium and chlorine NaCl , which forms deposits rock salt(Donbass, Solikamsk, Sol-Iletsk, etc.) Sodium chloride is also contained in sea water and salt springs. Typically, the upper layers of deposits contain potassium salts. They are present in sea water, but in much smaller quantities than sodium salts. The world's largest reserves of potassium salts are located in the Urals near Solikamsk (minerals sylvinite NaCl * KCl * MgCl * 6H 2 O). Large deposits of potassium salts have been explored and exploited in Belarus (Soligorsk).
Sodium and potassium are among the common elements. Sodium content in earth's crust is 2.64%, potassium – 2.6%.
Preparation and use of sodium and potassium.
Sodium is produced by electrolysis of molten sodium chloride or sodium hydroxide. During electrolysis of the melt NaCl sodium is released at the cathode:
Na + + e - = Na
And on the anode there is chlorine:
2Cl – 2e - = Cl 2
During electrolysis of the melt NaOH sodium is released at the cathode (the reaction equation is given above), and water and oxygen are released at the anode:
4 OH - -- 4e - = 2H 2 O + O 2
Due to the high cost of sodium hydroxide, the main modern method sodium is produced by electrolysis of the melt NaCl.
Potassium can also be obtained by electrolysis of molten KCl and KOH. However, this method of obtaining potassium has not found widespread use due to technical difficulties(low current output, difficulty in ensuring safety). Modern industrial production potassium is based on the following reactions:
KCl + Na NaCl + K (a)
KOH + Na NaOH + K (b)
In method (a), sodium vapor is passed through molten potassium chloride at 800 0 C, and the released potassium vapors condense. In method (b), the interaction between molten potassium hydroxide and liquid sodium is carried out in countercurrent at 440 0 C in a nickel reaction column.
Using the same methods, an alloy of potassium and sodium is produced, which is used as a liquid metal coolant in nuclear reactors.
An alloy of potassium and sodium is also used as a reducing agent in the production of titanium.
Potassium and its compounds are widely used in various industries farms. Peroxide of element No. 19 is necessary in the production of certain dyes, in the hydrolysis of starch, in the production of gunpowder, and in the bleaching of fabrics. Air regeneration in spaceships And submarines carried out using the same sodium and potassium peroxides. You can't make soap without caustic alkalis. Moreover, the best liquid toiletries, as well as special medical grades, are obtained using caustic potassium. Potash in large quantities goes to glass production.
Physical properties.
Because in atoms alkali metals one outer electron is in 4 or more vacant orbitals, and the ionization energy of atoms is low, then a metallic bond arises between metal atoms. For a substance with metal bond characteristic metallic shine, ductility, softness, good electrical conductivity and thermal conductivity. Potassium and sodium have these properties.
Sodium and potassium are silvery-white metals, the density of the former is 0.97 g/cm 3, second - 0.86 g /cm 3 , very soft, easy to cut with a knife.
Natural sodium consists of one isotope , potassium – from two stable isotopes (0.01%). Research uses radioactive isotopes artificially obtained: , And .
Chemical properties.
Sodium and potassium atoms at chemical interaction easily give up valence electrons, becoming positively charged ions:Na+ and K+ . Both metals are strong reducing agents.
In air, sodium and potassium quickly oxidize, so they are stored under a layer of kerosene. They easily interact with many non-metals - halogens, sulfur, phosphorus, etc. They react violently with water. When heated, they form hydrides with hydrogen NaH, KH. Metal hydrides are easily decomposed by water to form the corresponding alkali and hydrogen:
NaH + H 2 O = NaOH + H 2
When sodium burns in excess oxygen, sodium peroxide is formed Na2O2 , which interacts with wet carbon dioxide air, releasing oxygen:
2 Na 2 O 2 + 2CO 2 = 2Na 2 CO 3 + O 2
This reaction is the basis for the use of sodium peroxide to produce oxygen in submarines and for air regeneration in enclosed spaces.
Caustic alkalis.
Caustic alkalis are hydroxides that are highly soluble in water. The most important of them NaOH and KOH.
Sodium hydroxide and potassium hydroxide – white, opaque, solid crystalline substances. They dissolve well in water, releasing a large amount of heat. In aqueous solutions they are almost completely dissociated and are strong alkalis. They exhibit all the properties of bases.
Solid hydroxides sodium and potassium and their aqueous solutions absorb carbon monoxide(IV):
NaOH + CO 2 = NaHCO 3
2NaOH + CO 2 = Na 2 CO 3 + H 2 O
or in another form:
OH - + CO 2 = HCO
2OH - + CO 2 = CO + H 2 O
Solid in air NaOH and KOH absorb moisture, due to which they are used as gas dehumidifiers.
In industry, sodium hydroxide and potassium hydroxide are obtained by electrolysis of concentrated solutions, respectively NaCl and KCl. In this case, chlorine and hydrogen are produced simultaneously. The cathode is an iron mesh, the anode is graphite.
Electrolysis circuit (for example KCl ) should be presented as follows: KCl completely dissociates into ions K + and Cl - . When passing electric current ions approach the cathode K+ , to the anode – chloride ions Cl - . Potassium among standard ones electrode potentials located before aluminum, and its ions are reduced (attach electrons) much more difficult than water molecules. Hydrogen ions H+ very little in solution. Therefore, water molecules are discharged at the cathode, releasing molecular hydrogen :
2 H 2 O + 2e - = H 2 + 2OH -
Chloride ions in concentrated solution give up electrons (oxidize) more easily than water molecules, so chloride ions are discharged at the anode:
2 Cl - – 2e - = Cl 2
General equation electrolysis of a solution in ionic form:
2 Cl - – 2e - = Cl 2 1
2H 2 O+2e - = H 2 +2OH - 1
2Cl - + 2H 2 O electrolysis H 2 + 2OH - + Cl 2
2KCl + 2H2O electrolysis H2 + 2KOH + Cl2
The electrolysis of the solution proceeds similarly. NaCl. A solution containing NaOH and NaCl , is subjected to evaporation, as a result of which sodium chloride precipitates (it has much lower solubility and it changes little with temperature), which is separated and used for further electrolysis. Sodium hydroxide is produced in very large quantities. It is one of the most important products of the main chemical industry. It is used for the purification of petroleum products - gasoline and kerosene, for the production of soap, artificial silk, paper, in the textile, leather, chemical industries, as well as in everyday life (caustic soda, caustic soda).
The more expensive product, potassium hydroxide, is used less frequently than NaOH.
Sodium and potassium salts.
Sodium forms salts with all acids. Almost all of its salts are soluble in water. The most important of them are sodium chloride ( salt), soda and sodium sulfate.
Sodium chloride NaCl – a necessary seasoning for food, used for canning food products, and also serves as a raw material for the production of sodium hydroxide, chlorine, of hydrochloric acid, soda, etc.
Sodium sulfate Na2SO4 used in the production of soda and glass. From aqueous solutions decahydrate hydrate crystallizes Na 2 SO 4 * 10H 2 O , called Glauber's salt. Glauber's salt is used in medicine as a laxative. Sodium salts (sodium ions) color the burner flame yellow. This is a very sensitive method for detecting sodium in compounds.
Potassium salts are used mainly as potash fertilizers. Potassium salts (potassium ions) color the burner flame in purple. However, in the presence of even minute amounts of sodium compounds, the violet color is masked by yellow. In this case, it can be seen through blue glass, which absorbs yellow rays.
List of used literature.
“Basics general chemistry ” . Yu.D. Tretyakov, Yu.G. Metlin. Moscow “ Education ” 1980
“A manual on chemistry for applicants to universities ” . G.P. Khomchenko. 1976
Essay
in chemistry
Subject : Potassium and sodium.
Completed :
11th grade student
71 schools
Sivakov Nikolay
Saint Petersburg
1. History of potassium and sodium. 3
2. Sodium and potassium in nature. 5
3. Preparation and use of sodium and potassium. 6
4. Physical properties. Chemical properties. 7
5. Caustic alkalis. 8
6. Sodium and potassium salts. 10
7. List of references 11
From the history of potassium and sodium.
The name "sodium" (English and French Sodium, German Natrium) comes from an ancient word common in Egypt, among the ancient Greeks (vixpov) and Romans. It is found in Pliny (Nitron) and other ancient authors and corresponds to the Hebrew neter. In ancient Egypt, natron, or nitron, was generally called an alkali obtained not only from natural soda lakes, but also from plant ash. It was used for washing, making glazes, and mummifying corpses. In the Middle Ages, the name nitron (nitron, natron, nataron), as well as boron (baurach), also applied to saltpeter (Nitrum). Arab alchemists called alkali alkali. With the discovery of gunpowder in Europe, saltpeter (Sal Petrae) began to be strictly distinguished from alkalis, and in the 17th century. already distinguished between non-volatile, or fixed alkalis, and volatile alkali (Alkali volatile). At the same time, a difference was established between vegetable (Alkali fixum vegetabile - potash) and mineral alkali (Alkali fixum minerale - soda). At the end of the 18th century. Klaproth introduced the name natron, or soda, for the mineral alkali and for the vegetable alkali - potassium (Kali), Lavoisier did not place alkalis in the "Table of Simple Bodies", indicating in a note to it that these were probably complex substances that once Someday they will be decomposed. Indeed, in 1807 Davy, by electrolysis of slightly moistened solid alkalis, obtained free metals - potassium and sodium, calling them potassium and sodium. The following year, Gilbert, publisher of the famous Annals of Physics, proposed calling the new metals potassium and sodium (Natronium); Berzelius shortened the latter name to "sodium" (Natrium). At the beginning of the 19th century. in Russia sodium was called sodia (Dvigubsky, 182i; Solovyov, 1824); Strakhov proposed the name sod (1825). Sodium salts were called, for example, soda sulfate, hydrochloric soda, and at the same time acetic soda (Dvigubsky, 1828). Hess, following the example of Berzelius, introduced the name sodium.
Potassium (English Potassium, French Potassium, German Kalium) was discovered in 1807 by Davy, who performed the electrolysis of solid, slightly moistened caustic potassium. Davy called the new metal Potassium, but this name did not stick. The godfather of metal turned out to be Gilbert, the famous publisher of the magazine "Annalen de Physik", who proposed the name "potassium"; it was adopted in Germany and Russia. Both names come from terms that were used long before the discovery of potassium metal. The word potassium is derived from the word potash, which probably appeared in the 16th century. It is found in Van Helmont in the second half of the 17th century. is widely used as the name of a commercial product - potash - in Russia, England and Holland. Translated into Russian, the word potashe means “pot ash or ash boiled in a pot”; in the XVI - XVII centuries. potash was obtained in huge quantities from wood ash, which was boiled in large boilers. Potash was used to prepare mainly liter (purified) saltpeter, which was used to make gunpowder. Especially a lot of potash was produced in Russia, in the forests near Arzamas and Ardatov in mobile factories (Maidans) that belonged to a relative of Tsar Alexei Mikhailovich, a close boyar B.I. Morozov. As for the word potassium, it comes from the Arabic term alkali (alkaline substances). In the Middle Ages, alkalis, or, as they said then, alkaline salts, were almost indistinguishable from each other and were called by names that had the same meaning: natron, borax, varek, etc. The word kali (qila) was found around 850 Arab writers, then the word Qali (al-Qali) began to be used, which denoted a product obtained from the ash of some plants; the Arabic qiljin or qaljan (ash) and qalaj (burn) are associated with these words. In the era of atrochemistry, alkalis began to be divided into “fixed” and “volatile”. In the 17th century There are names alkali fixum minerale (mineral fixed alkali or caustic soda), alkali fixum. vegetabile (vegetable fixed alkali or potash and caustic potassium), as well as alkali volatile (volatile alkali or NH 3). Black established a distinction between caustic and soft, or carbonic, alkalis. Alkalies do not appear in the Table of Simple Bodies, but in a note to the table Lavoisier indicates that the fixed alkalis (potash and soda) are probably complex substances, although the nature of their constituent parts has not yet been studied. In Russian chemical literature of the first quarter of the 19th century. potassium was called potassium (Soloviev, 1824), potash (Strakhovy, 1825), potash (Shcheglov, 1830); in the "Dvigubsky Store" already in 1828. Along with the name potash (potash sulfate), the name potassium (caustic potassium, hydrochloric potassium, etc.) is found. The name potassium became generally accepted after the publication of Hess's textbook.
Sodium and potassium.
Alkali metals are not found in free form in nature. Sodium and potassium are found in various compounds. The most important is the compound of sodium with chlorine NaCl, which forms rock salt deposits (Donbass, Solikamsk, Sol-Iletsk, etc.). Sodium chloride is also found in sea water and salt springs. Typically, the upper layers of deposits contain potassium salts. They are present in sea water, but in much smaller quantities than sodium salts. The world's largest reserves of potassium salts are located in the Urals near Solikamsk (minerals sylvinite NaCl * KCl * MgCl * 6H 2 O). Large deposits of potassium salts have been explored and exploited in Belarus (Soligorsk).
Sodium and potassium are among the common elements. The sodium content in the earth's crust is 2.64%, potassium - 2.6%.
Preparation and use of sodium and potassium.
Sodium is produced by electrolysis of molten sodium chloride or sodium hydroxide. During the electrolysis of a NaCl melt, sodium is released at the cathode:
Na + + e - = Na
And on the anode there is chlorine:
2Cl – 2e - = Cl 2
During the electrolysis of a NaOH melt, sodium is released at the cathode (the reaction equation is given above), and water and oxygen are released at the anode:
4OH - -- 4e - = 2H 2 O + O 2
Due to the high cost of sodium hydroxide, the main modern method for producing sodium is the electrolysis of NaCl melt.
Potassium can also be obtained by electrolysis of molten KCl and KOH. However, this method of obtaining potassium has not found widespread use due to technical difficulties (low current efficiency, difficulty in ensuring safety precautions). Modern industrial production of potassium is based on the following reactions:
KCl + Na Û NaCl + K (a)
KOH + Na Û NaOH + K (b)
In method (a), sodium vapor is passed through molten potassium chloride at 800 0 C, and the released potassium vapor is condensed. In method (b), the interaction between molten potassium hydroxide and liquid sodium is carried out in countercurrent at 440 0 C in a nickel reaction column.
Using the same methods, an alloy of potassium and sodium is produced, which is used as a liquid metal coolant in nuclear reactors.
An alloy of potassium and sodium is also used as a reducing agent in the production of titanium.
Potassium and its compounds are widely used in various sectors of the economy. Peroxide of element No. 19 is necessary in the production of certain dyes, in the hydrolysis of starch, in the production of gunpowder, and in the bleaching of fabrics. Air regeneration in spaceships and submarines is carried out using the same sodium and potassium peroxides. You can't make soap without caustic alkalis. Moreover, the best liquid toiletries, as well as special medical grades, are obtained using caustic potassium. Potash is used in large quantities for glass production.
Physical properties.
Since in alkali metal atoms one outer electron is shared by 4 or more free orbitals, and the ionization energy of the atoms is low, a metallic bond arises between the metal atoms. A substance with a metallic bond is characterized by metallic luster, ductility, softness, good electrical conductivity and thermal conductivity. Potassium and sodium have these properties.
Sodium and potassium are silvery-white metals, the density of the first is 0.97 g/cm 3, the second is 0.86 g/cm 3, very soft, easy to cut with a knife.
Natural sodium consists of one isotope, potassium - of two stable isotopes (0.01%). In research, radioactive isotopes obtained artificially are used:, and.
Chemical properties.
During chemical interaction, sodium and potassium atoms easily give up valence electrons, turning into positively charged ions: Na + and K +. Both metals are strong reducing agents.
In air, sodium and potassium quickly oxidize, so they are stored under a layer of kerosene. They easily interact with many non-metals - halogens, sulfur, phosphorus, etc. They react violently with water. With hydrogen, when heated, they form hydrides NaH, KH. Metal hydrides are easily decomposed by water to form the corresponding alkali and hydrogen:
NaH + H 2 O = NaOH + H 2
When sodium burns in excess oxygen, sodium peroxide Na 2 O 2 is formed, which reacts with moist carbon dioxide in the air, releasing oxygen:
2Na 2 O 2 + 2CO 2 = 2Na 2 CO 3 + O 2
This reaction is the basis for the use of sodium peroxide to produce oxygen in submarines and for air regeneration in enclosed spaces.
Caustic alkalis.
Caustic alkalis are hydroxides that are highly soluble in water. The most important of them are NaOH and KOH.
Sodium hydroxide and potassium hydroxide are white, opaque, crystalline solids. They dissolve well in water, releasing a large amount of heat. In aqueous solutions they are almost completely dissociated and are strong alkalis. They exhibit all the properties of bases.
Solid sodium and potassium hydroxides and their aqueous solutions absorb carbon monoxide (IV):
NaOH + CO 2 = NaHCO 3
2NaOH + CO 2 = Na 2 CO 3 + H 2 O
or in another form:
OH - + CO 2 = HCO
2OH - + CO 2 = CO + H 2 O
In the solid state in air, NaOH and KOH absorb moisture, which is why they are used as gas desiccants.
In industry, sodium hydroxide and potassium hydroxide are obtained by electrolysis of concentrated solutions of NaCl and KCl, respectively. In this case, chlorine and hydrogen are produced simultaneously. The cathode is an iron mesh, the anode is graphite.
The electrolysis scheme (using KCl as an example) should be represented as follows: KCl completely dissociates into K + and Cl - ions. When an electric current passes, K + ions approach the cathode, and Cl - chloride ions approach the anode. In the series of standard electrode potentials, potassium is located before aluminum, and its ions are reduced (gaining electrons) much more difficult than water molecules. There are very few hydrogen ions H + in the solution. Therefore, water molecules are discharged at the cathode, releasing molecular hydrogen:
2H 2 O + 2e - = H 2 + 2OH -
Chloride ions in a concentrated solution give up electrons (oxidize) more easily than water molecules, so chloride ions are discharged at the anode:
2Cl - – 2e - = Cl 2
The general equation for the electrolysis of a solution in ionic form is:
2Cl - – 2e - = Cl 2 1
2H 2 O + 2e - = H 2 + 2OH - 1
2Cl - + 2H 2 O electrolysis H 2 + 2OH - + Cl 2
2KCl + 2H2O electrolysis H2 + 2KOH + Cl2
Electrolysis of a NaCl solution proceeds similarly. A solution containing NaOH and NaCl is evaporated, resulting in sodium chloride precipitating (it has much lower solubility and it varies little with temperature), which is separated and used for further electrolysis. Sodium hydroxide is produced in very large quantities. It is one of the most important products of the main chemical industry. It is used for the purification of petroleum products - gasoline and kerosene, for the production of soap, artificial silk, paper, in the textile, leather, chemical industries, as well as in everyday life (caustic soda, caustic soda).
The more expensive product, potassium hydroxide, is used less frequently than NaOH.
Sodium and potassium salts.
Sodium forms salts with all acids. Almost all of its salts are soluble in water. The most important of them are sodium chloride (table salt), soda and sodium sulfate.
Sodium chloride NaCl is a necessary food seasoning, used for food preservation, and also serves as a raw material for the production of sodium hydroxide, chlorine, hydrochloric acid, soda, etc.
Sodium sulfate Na 2 SO 4 is used in the production of soda and glass. The decahydrate hydrate Na 2 SO 4 * 10H 2 O, called Glauber's salt, crystallizes from aqueous solutions. Glauber's salt is used in medicine as a laxative. Sodium salts (sodium ions) turn the burner flame yellow. This is a very sensitive method for detecting sodium in compounds.
Potassium salts are used mainly as potash fertilizers. Potassium salts (potassium ions) turn the burner flame purple. However, in the presence of even minute amounts of sodium compounds, the violet color is masked by yellow. In this case, it can be seen through blue glass, which absorbs yellow rays.
List of used literature.
1. “ Basics general chemistry ” . Yu.D. Tretyakov, Yu.G. Metlin. Moscow “ Education ” 1980
2. “ A manual on chemistry for applicants to universities ” . G.P. Khomchenko. 1976
Here there is a shift in the equilibrium of reactions towards the formation of products.
Sodium and Potassium as representatives of alkali metals: atomic structure, distribution in nature. Physical and Chemical properties sodium and potassium. Extraction, use of sodium and potassium
Sodium and Potassium are elements main subgroup i groups periodic table chemical elements by D. I. Mendeleev. At the outer energy level of the atoms of these elements there is 1 unpaired s-electron. Trying to complete the outer energy level, the atoms of these elements energetically give up one electron and exhibit the properties of active reducing agents. In their compounds, these elements are monovalent. Therefore, Sodium and Potassium are typical representatives of the alkali metal elements.
In nature, alkaline elements are found only in the form of salts. The most important minerals of Sodium are rock salt or halite NaCl, Chilean saltpeter NaNO 3, Glauber's salt or mirabilite Na 2 SO 4 · 10H 2 O. A large amount of Sodium salts crystallize during the evaporation of sea water. The mass fraction of Sodium in the earth's crust is 2.6%. Potassium, like Sodium, is quite common chemical element. Mass fraction Potassium in the earth's crust - 2.5%. Natural salts of Potassium - sylvin KCl, sylvinite KCl · NaCl, carnallite KCl · MgCl 2 · 6H 2 O. Potassium is part of feldspars and mica.
The cations Sodium and Potassium play important role in the life of living organisms. Sodium is found in bone tissue, blood, brain, lungs, eye fluid, and cerebrospinal fluid. Sodium cations are involved in maintaining osmotic pressure and acid-base balance, in conducting nerve impulses. Potassium is found in bone tissue, muscles, blood, brain, heart, kidneys. Potassium cations take part in conducting bioelectric potentials in nerves and muscles, in regulating contractions of the heart and other muscles, maintaining osmotic pressure in cells, and activating some enzymes.
In terms of physical properties, sodium and potassium are typical metals. They have a silvery-white color, high electrical conductivity and thermal conductivity. They differ in that they are quite plastic, soft (easy to cut with a knife), light (float on the surface of the water) and fusible. Fresh cuts of sodium and potassium are shiny. These metals are very active, so they are stored under a layer of kerosene or in sealed ampoules.
Sodium and potassium have high chemical activity and are strong reducing agents. In air, sodium and potassium are easily oxidized. The reaction products are the corresponding oxides and peroxides of these elements:
4Na + O 2 = 2Na 2 O
2Na + O 2 = Na 2 O 2
4K + O 2 = 2K 2 O K +O 2 = KO 2.
Sodium and potassium react actively with halogens, releasing light. When sodium reacts with chlorine, sodium chloride is formed:
2Na + Cl 2 = 2NaCl.
The products of reactions of sodium and potassium with sulfur are sulfides of these elements, for example:
2K + S = K 2 S.
When sodium and potassium interact with water, the corresponding meadow and hydrogen gas are formed.
Sodium reacts quite actively with water:
2Na + 2H 2 O = 2NaOH +H 2.
The reaction of potassium with water occurs even more actively with the possible spontaneous combustion of hydrogen:
2K + 2H 2 O = 2KOH +H 2.
Sodium and potassium are produced by electrolysis of molten chlorides and hydroxides of these elements. Sodium and potassium were first obtained in 1807 by the English scientist Humphry Davy.
Sodium is used as a filler in gas-discharge lamps. In metallurgy, some are reduced with sodium rare metals: titanium, zirconium, tantalum. Potassium is used in solar cells. Sodium, potassium and their alloys are used as coolants in nuclear power plants. Potassium is important element for plant development, and is applied to the soil in the form of potassium fertilizers.
Sodium and potassium as representatives of alkali metals: atomic structure, distribution in nature. Physical and chemical properties of sodium and potassium. Extraction and use of sodium and potassium
Sodium and potassium are elements of the main subgroup of group I of the periodic system of chemical elements of D.I. Mendeleev. At the outer energy level of the atoms of these elements there is 1 unpaired s-electron. Trying to complete the outside energy level, the atoms of these elements energetically give up one electron and exhibit the properties of active reducing agents. In their compounds, these elements are monovalent. So, Sodium and potassium are typical representatives of the alkali metal elements.
In nature alkaline elements found only in the form of salts. The most important minerals of sodium are rock salt or halite NaCl, Chilean saltpeter NaNO 3, Glauber's salt or mirabilite Na 2 SO 4 10H 2 O. A large number of sodium salts crystallize during the evaporation of sea water. The mass fraction of sodium in the earth's crust is 2.6%. Potassium, like sodium, is a fairly common chemical element. The mass fraction of potassium in the earth's crust is 2.5%. Natural potassium salts are sylvin KCl, sylvinite KCl NaCl, carnallite KCl MgCl 2 6H 2 O. Potassium is part of feldspars and mica.
Sodium and potassium cations play an important role in the life of living organisms. Sodium is found in bone tissue, blood, brain, lungs, eye fluid, and cerebrospinal fluid. Sodium cations are involved in maintaining osmotic pressure and acid-base balance, and in conducting nerve impulses. Potassium is found in bone tissue, muscles, blood, brain, heart, kidneys. Potassium cations are involved in conducting bioelectric potentials in nerves and muscles, in regulating contractions of the heart and other muscles, maintaining osmotic pressure in cells, and activating certain enzymes.
In terms of physical properties, sodium and potassium are typical metals. They are silver-white in color, have high electrical conductivity and thermal conductivity. They differ in that they are quite plastic, soft (easy to cut with a knife), lightweight (float on the surface of the water) and fusible. Fresh cuts of sodium and potassium are shiny. These metals are very active, so they are stored under a layer of kerosene, or in sealed ampoules.
Sodium and potassium are highly reactive and are strong reducing agents. In air, sodium and potassium are easily oxidized. The reaction products are the corresponding oxides and peroxides of these elements:
4Na + O 2 = 2Na 2 O
2Na + O 2 = Na 2 O 2
4K + O 2 = 2K 2 O K + O 2 = KO 2.
Sodium and potassium react actively with halogens, releasing light. When sodium reacts with chlorine, sodium chloride is formed:
2Na + Cl 2 = 2NaCl.
The products of reactions of sodium and potassium with sulfur are sulfides of these elements, for example:
When sodium and potassium interact with water, a corresponding meadow is formed and hydrogen gases.
Sodium reacts quite actively with water:
2Na + 2H 2 O = 2NaOH + H 2.
The reaction of potassium with water occurs even more actively with the possible spontaneous combustion of hydrogen:
2K + 2H 2 O = 2KOH + H 2.
Sodium and potassium are produced by electrolysis of molten chlorides and hydroxides of these elements. Sodium and potassium were first obtained in 1807 by the English scientist Humphry Davy.
Sodium is used as a filler in gas-discharge lamps. In metallurgy, sodium is used to reduce some rare metals: titanium, zirconium, tantalum. Potassium is used in solar cells. Sodium, potassium and their alloys are used as coolants in nuclear power plants. Potassium is an important element for plant development and is added to the soil in the form of potassium fertilizers.
1. History of potassium and sodium.
2. Sodium and potassium in nature.
3. Preparation and use of sodium and potassium.
4. Physical properties. Chemical properties.
5. Caustic alkalis.
6. Sodium and potassium salts.
7. List of references used
From the history of potassium and sodium.
The name "sodium" (English and French Sodium, German Natrium) comes from an ancient word common in Egypt, among the ancient Greeks (vixpov) and Romans. It is found in Pliny (Nitron) and other ancient authors and corresponds to the Hebrew neter. In ancient Egypt, natron, or nitron, was generally called an alkali obtained not only from natural soda lakes, but also from plant ash. It was used for washing, making glazes, and mummifying corpses. In the Middle Ages, the name nitron (nitron, natron, nataron), as well as boron (baurach), also applied to saltpeter (Nitrum). Arab alchemists called alkali alkali. With the discovery of gunpowder in Europe, saltpeter (Sal Petrae) began to be strictly distinguished from alkalis, and in the 17th century. already distinguished between non-volatile, or fixed alkalis, and volatile alkali (Alkali volatile). At the same time, a difference was established between vegetable (Alkali fixum vegetabile - potash) and mineral alkali (Alkali fixum minerale - soda). At the end of the 18th century. Klaproth introduced the name natron, or soda, for the mineral alkali and for the vegetable alkali - potassium (Kali), Lavoisier did not place alkalis in the "Table of Simple Bodies", indicating in a note to it that these were probably complex substances that once Someday they will be decomposed. Indeed, in 1807 Davy, by electrolysis of slightly moistened solid alkalis, obtained free metals - potassium and sodium, calling them potassium and sodium. The following year, Gilbert, publisher of the famous Annals of Physics, proposed calling the new metals potassium and sodium (Natronium); Berzelius shortened the latter name to "sodium" (Natrium). At the beginning of the 19th century. in Russia sodium was called sodia (Dvigubsky, 182i; Solovyov, 1824); Strakhov proposed the name sod (1825). Sodium salts were called, for example, soda sulfate, hydrochloric soda, and at the same time acetic soda (Dvigubsky, 1828). Hess, following the example of Berzelius, introduced the name sodium.
Potassium (English Potassium, French Potassium, German Kalium) was discovered in 1807 by Davy, who performed the electrolysis of solid, slightly moistened caustic potassium. Davy called the new metal Potassium, but this name did not stick. The godfather of metal turned out to be Gilbert, the famous publisher of the magazine "Annalen de Physik", who proposed the name "potassium"; it was adopted in Germany and Russia. Both names come from terms that were used long before the discovery of potassium metal. The word potassium is derived from the word potash, which probably appeared in the 16th century. It is found in Van Helmont in the second half of the 17th century. is widely used as the name of a commercial product - potash - in Russia, England and Holland. Translated into Russian, the word potashe means “pot ash or ash boiled in a pot”; in the XVI - XVII centuries. potash was obtained in huge quantities from wood ash, which was boiled in large boilers. Potash was used to prepare mainly liter (purified) saltpeter, which was used to make gunpowder. Especially a lot of potash was produced in Russia, in the forests near Arzamas and Ardatov in mobile factories (Maidans) that belonged to a relative of Tsar Alexei Mikhailovich, a close boyar B.I. Morozov. As for the word potassium, it comes from the Arabic term alkali (alkaline substances). In the Middle Ages, alkalis, or, as they said then, alkaline salts, were almost indistinguishable from each other and were called by names that had the same meaning: natron, borax, varek, etc. The word kali (qila) was found around 850 Arab writers, then the word Qali (al-Qali) began to be used, which denoted a product obtained from the ash of some plants; the Arabic qiljin or qaljan (ash) and qalaj (burn) are associated with these words. In the era of atrochemistry, alkalis began to be divided into “fixed” and “volatile”. In the 17th century There are names alkali fixum minerale (mineral fixed alkali or caustic soda), alkali fixum. vegetabile (vegetable fixed alkali or potash and caustic potassium), as well as alkali volatile (volatile alkali or NH3). Black established a distinction between caustic and soft, or carbonic, alkalis. Alkalies do not appear in the Table of Simple Bodies, but in a note to the table Lavoisier indicates that the fixed alkalis (potash and soda) are probably complex substances, although the nature of their constituent parts has not yet been studied. In Russian chemical literature of the first quarter of the 19th century. potassium was called potassium (Soloviev, 1824), potash (Strakhovy, 1825), potash (Shcheglov, 1830); in the "Dvigubsky Store" already in 1828. Along with the name potash (potash sulfate), the name potassium (caustic potassium, hydrochloric potassium, etc.) is found. The name potassium became generally accepted after the publication of Hess's textbook.
Sodium and potassium.
Alkali metals are not found in free form in nature. Sodium and potassium are found in various compounds. The most important is the compound of sodium with chlorine NaCl, which forms rock salt deposits (Donbass, Solikamsk, Sol-Iletsk, etc.). Sodium chloride is also found in sea water and salt springs. Typically, the upper layers of deposits contain potassium salts. They are present in sea water, but in much smaller quantities than sodium salts. The world's largest reserves of potassium salts are located in the Urals near Solikamsk (minerals sylvinite NaCl * KCl * MgCl * 6H2O). Large deposits of potassium salts have been explored and exploited in Belarus (Soligorsk).
Sodium and potassium are among the common elements. The sodium content in the earth's crust is 2.64%, potassium - 2.6%.
Preparation and use of sodium and potassium.
Sodium is produced by electrolysis of molten sodium chloride or sodium hydroxide. During the electrolysis of a NaCl melt, sodium is released at the cathode:
And on the anode there is chlorine:
2Cl – 2e- = Cl2
During the electrolysis of a NaOH melt, sodium is released at the cathode (the reaction equation is given above), and water and oxygen are released at the anode:
4OH- -- 4e- = 2H2O + O2
Due to the high cost of sodium hydroxide, the main modern method for producing sodium is the electrolysis of NaCl melt.
Potassium can also be obtained by electrolysis of molten KCl and KOH. However, this method of obtaining potassium has not found widespread use due to technical difficulties (low current efficiency, difficulty in ensuring safety precautions). Modern industrial production of potassium is based on the following reactions:
KCl + Na Û NaCl + K (a)