Potassium is the nineteenth element of the periodic table and belongs to the alkali metals. This is a simple substance that, under normal conditions, is in a solid state of aggregation. Potassium boils at a temperature of 761 °C. The melting point of the element is 63 °C. Potassium has a silvery-white color with a metallic sheen.
Chemical properties of potassium
Potassium is highly chemically active, so it cannot be stored in the open air: the alkali metal instantly reacts with surrounding substances. This chemical element belongs to group I and period IV of the periodic table. Potassium has all the properties characteristic of metals.
It interacts with simple substances, which include halogens (bromine, chlorine, fluorine, iodine) and phosphorus, nitrogen and oxygen. The interaction of potassium with oxygen is called oxidation. During this chemical reaction, oxygen and potassium are consumed in a 4:1 molar ratio, resulting in the formation of two parts potassium oxide. This interaction can be expressed by the reaction equation:
4K + O₂ = 2K₂O
When potassium burns, a bright purple flame is observed.
This interaction is considered a qualitative reaction for the determination of potassium. Reactions of potassium with halogens are named according to the names of the chemical elements: fluorination, iodination, bromination, chlorination. Such interactions are addition reactions. An example is the reaction between potassium and chlorine, resulting in the formation of potassium chloride. To carry out such an interaction, take two moles of potassium and one mole. As a result, two moles of potassium are formed:
2К + СІ₂ = 2КІ
Molecular structure of potassium chlorideWhen burning in open air, potassium and nitrogen are consumed in a molar ratio of 6:1. As a result of this interaction, potassium nitride is formed in the amount of two parts:
6K + N₂ = 2K₃N
The compound appears as green-black crystals. Potassium reacts with phosphorus according to the same principle. If you take 3 moles of potassium and 1 mole of phosphorus, you get 1 mole of phosphide:
3К + Р = К₃Р
Potassium reacts with hydrogen to form a hydride:
2K + N₂ = 2KN
All addition reactions occur at high temperatures
Interaction of potassium with complex substances
Complex substances with which potassium reacts include water, salts, acids and oxides. Since potassium is a reactive metal, it displaces hydrogen atoms from their compounds. An example is the reaction that occurs between potassium and hydrochloric acid. To carry it out, 2 moles of potassium and acid are taken. As a result of the reaction, 2 moles of potassium chloride and 1 mole of hydrogen are formed:
2K + 2НІ = 2КІ + Н₂
It is worth considering in more detail the process of interaction of potassium with water. Potassium reacts violently with water. It moves along the surface of the water, pushed by the released hydrogen:
2K + 2H₂O = 2KOH + H₂
During the reaction, a lot of heat is released per unit time, which leads to the ignition of potassium and released hydrogen. This is a very interesting process: upon contact with water, potassium instantly ignites, a violet flame crackles and quickly moves along the surface of the water. At the end of the reaction, a flash occurs with splashing drops of burning potassium and reaction products.
Reaction of potassium with water
The main end product of the reaction of potassium with water is potassium hydroxide (alkali). Equation for the reaction of potassium with water:
4K + 2H₂O + O₂ = 4KOH
Attention! Do not try to repeat this experience yourself!
If the experiment is carried out incorrectly, you can get burned by alkali. For the reaction, a crystallizer with water is usually used, into which a piece of potassium is placed. As soon as the hydrogen stops burning, many people want to look into the crystallizer. At this moment, the final stage of the reaction of potassium with water occurs, accompanied by a weak explosion and splashing of the resulting hot alkali. Therefore, for safety reasons, it is worth keeping a certain distance from the laboratory bench until the reaction is completely completed. you will find the most spectacular experiments that you can do with your children at home.
The structure of potassium
A potassium atom consists of a nucleus containing protons and neutrons, and electrons orbiting around it. The number of electrons is always equal to the number of protons inside the nucleus. When an electron is removed or added to an atom, it ceases to be neutral and becomes an ion. Ions are divided into cations and anions. Cations have a positive charge, anions have a negative charge. When an electron is added to an atom, it becomes an anion; if one of the electrons leaves its orbit, the neutral atom turns into a cation.
The serial number of potassium in the periodic table is 19. This means that there are also 19 protons in the nucleus of a chemical element. Conclusion: there are 19 electrons around the nucleus. The number of protons in the structure is determined as follows: subtract the serial number of the chemical element from the atomic mass. Conclusion: there are 20 protons in the potassium nucleus. Potassium belongs to the IV period, has 4 “orbits” in which electrons are evenly distributed and are in constant motion. The first “orbit” contains 2 electrons, the second - 8; in the third and last, fourth “orbit”, 1 electron rotates. This explains the high level of chemical activity of potassium: its last “orbit” is not completely filled, so the element tends to combine with other atoms. As a result, the electrons in the last orbits of the two elements will become common.
This article will characterize potassium from the point of view of physics and chemistry. The first of these sciences studies the mechanical and external properties of substances. And the second is their interaction with each other - this is chemistry. Potassium is the nineteenth element in the periodic table. It belongs to This article will consider the electronic formula of potassium, its behavior with other substances, etc. This is one of the most active metals. The science that studies this and other elements is chemistry. Grade 8 involves studying their properties. Therefore, this article will be useful for schoolchildren. So, let's begin.
Characteristics of potassium in terms of physics
This is a simple substance that, under normal conditions, is in a solid state of aggregation. The melting point is sixty-three degrees Celsius. This metal boils when the temperature reaches seven hundred and sixty-one degrees Celsius. The substance in question has a silvery-white color. Has a metallic luster.
The density of potassium is eighty-six hundredths of a gram per cubic centimeter. This is a very light metal. The formula of potassium is very simple - it does not form molecules. This substance consists of atoms that are located close to each other and have a crystal lattice. The atomic mass of potassium is thirty-nine grams per mole. Its hardness is very low - it can be easily cut with a knife, like cheese.
Potassium and chemistry
Let's start with the fact that potassium is a chemical element that has very high chemical activity. You can’t even store it in the open air, as it instantly begins to react with the substances around it. Potassium is a chemical element that belongs to the first group and the fourth period of the periodic table. It has all the properties that are characteristic of metals.
Interaction with simple substances
These include: oxygen, nitrogen, sulfur, phosphorus, halogens (iodine, fluorine, chlorine, bromine). Let's consider the interaction of potassium with each of them in order. Interaction with oxygen is called oxidation. During this chemical reaction, potassium and oxygen are consumed in a molar ratio of four parts to one, resulting in the formation of an oxide of the metal in question in an amount of two parts. This interaction can be expressed using the following reaction equation: 4K + O2 = 2K2O. When potassium burns, you can observe
Therefore, this reaction is considered qualitative for the determination of potassium. Reactions with halogens are named according to the names of these chemical elements: iodination, fluorination, chlorination, bromination. These interactions can be called addition reactions, since atoms of two different substances combine into one. An example of such a process is the reaction between potassium and chlorine, which results in the formation of chloride of the metal in question. To carry out this interaction, it is necessary to take two of these components - two moles of the first and one mole of the second. As a result, two moles of the potassium compound are formed. This reaction is expressed by the following equation: 2K + CI2 = 2KCI. With nitrogen, potassium can form compounds when burned in the open air. During this reaction, the metal in question and nitrogen are consumed in a molar ratio of six parts to one; as a result of this interaction, potassium nitride is formed in an amount of two parts. This can be shown as the following equation: 6K + N2 = 2K3N. This compound is a green-black crystals. With phosphorus, the metal in question reacts according to the same principle. If we take three moles of potassium and one mole of phosphorus, we get one mole of phosphide. This chemical interaction can be written in the form of the following reaction equation: 3K + P = K3P. In addition, potassium is able to react with hydrogen, forming a hydride. As an example, the following equation can be given: 2K + H2 = 2KN. All addition reactions occur only in the presence of high temperatures.
Interaction with complex substances
The characteristics of potassium from a chemical point of view include consideration of this topic. The types of compounds that potassium can react with include water, acids, salts, and oxides. The metal in question reacts differently with all of them.
Potassium and water
This chemical element reacts violently with it. This produces hydroxide as well as hydrogen. If we take two moles of potassium and water, we get the same amount and one mole of hydrogen. This chemical interaction can be expressed using the following equation: 2K + 2H2O = 2KOH = H2.
Reactions with acids
Since potassium is an active metal, it easily displaces hydrogen atoms from their compounds. An example would be a reaction that occurs between the substance in question and hydrochloric acid. To carry it out, you need to take two moles of potassium, as well as acid in the same amount. As a result, two moles and hydrogen are formed - one mole. This process can be written by the following equation: 2K + 2НІ = 2КІ + Н2.
Potassium and oxides
The metal in question reacts with this group of inorganic substances only upon significant heating. If the metal atom that is part of the oxide is more passive than the one we are talking about in this article, essentially an exchange reaction occurs. For example, if you take two moles of potassium and one mole of cuprum oxide, then as a result of their interaction you can get one mole of the oxide of the chemical element in question and pure cuprum. This can be shown in the form of the following equation: 2K + CuO = K2O + Cu. This is where the powerful reducing properties of potassium come into play.
Interaction with bases
Potassium is capable of reacting with metal hydroxides that are to the right of it in the electrochemical activity series. In this case, its restorative properties also appear. For example, if we take two moles of potassium and one mole of barium hydroxide, then as a result of the substitution reaction we will obtain substances such as potassium hydroxide in an amount of two moles and pure barium (one mole) - it will precipitate. The chemical interaction presented can be represented as the following equation: 2K + Ba(OH)2 = 2KOH + Ba.
Reactions with salts
In this case, potassium still exhibits its properties as a strong reducing agent. By replacing atoms of chemically more passive elements, it makes it possible to obtain pure metal. For example, if you add three moles of potassium to an amount of two moles, then as a result of this reaction we get three moles of potassium chloride and two moles of aluminum. This process can be expressed using the equation as follows: 3К + 2АІСІ3 = 3КІ2 + 2АІ.
Reactions with fats
If you add potassium to any organic substance of this group, it will also displace one of the hydrogen atoms. For example, when stearin is mixed with the metal in question, potassium stearate and hydrogen are formed. The resulting substance is used to make liquid soap. This is where the characterization of potassium and its interactions with other substances ends.
Use of potassium and its compounds
Like all metals, the one discussed in this article is necessary for many industrial processes. The main use of potassium occurs in the chemical industry. Due to its high chemical activity, pronounced alkali metal and reducing properties, it is used as a reagent for many interactions and the production of various substances. In addition, alloys containing potassium are used as coolants in nuclear reactors. The metal discussed in this article also finds its application in electrical engineering. In addition to all of the above, it is one of the main components of plant fertilizers. In addition, its compounds are used in a wide variety of industries. Thus, in gold mining, potassium cyanide is used, which serves as a reagent for separating valuable metals from ores. Phosphates of the chemical element in question are used in glass production and are components of all kinds of cleaning products and powders. Matches contain chlorate of this metal. In the manufacture of films for old cameras, bromide of the element in question was used. As you already know, it can be obtained by bromination of potassium at high temperatures. In medicine, the chloride of this chemical element is used. In soap making - stearate and other fat derivatives.
Obtaining the metal in question
Nowadays, potassium is extracted in laboratories in two main ways. The first is its reduction from hydroxide with the help of sodium, which is chemically even more active than potassium. And the second is to obtain it from chloride, also with the help of sodium. If you add the same amount of sodium to one mole of potassium hydroxide, one mole of sodium alkali and pure potassium are formed. The equation for this reaction is as follows: KOH + Na = NaOH + K. To carry out the second type of reaction, you need to mix the chloride of the metal in question and sodium in equal molar proportions. As a result of this, substances such as kitchen salt and potassium are formed in the same ratio. This chemical interaction can be expressed using the following reaction equation: KCI + Na = NaCl + K.
The structure of potassium
The atom of this chemical element, like all others, consists of a nucleus that contains protons and neutrons, as well as electrons that revolve around it. The number of electrons is always equal to the number of protons that are inside the nucleus. If any electron is detached or attached to an atom, then it ceases to be neutral and turns into an ion. They come in two types: cations and anions. The former have a positive charge, while the latter have a negative charge. If an electron is added to an atom, it turns into an anion, but if any of the electrons leaves its orbit, the neutral atom becomes a cation. Since the serial number of potassium, according to the periodic table, is nineteen, there are the same number of protons in the nucleus of this chemical element. Therefore, we can conclude that there are nineteen electrons around the nucleus. The number of protons contained in the structure of an atom can be determined by subtracting the atomic number of the chemical element from the atomic mass. So we can conclude that there are twenty protons in the potassium nucleus. Since the metal considered in this article belongs to the fourth period, it has four orbits in which electrons are evenly distributed, which are constantly in motion. The diagram of potassium is as follows: the first orbit has two electrons, the second has eight; just like in the third, in the last, fourth, orbit only one electron rotates. This explains the high level of chemical activity of this metal - its last orbit is not completely filled, so it tends to combine with some other atoms, as a result of which the electrons of their last orbits will become common.
Where can this element be found in nature?
Since it has extremely high chemical activity, it is not found anywhere on the planet in its pure form. It can only be seen in various compounds. potassium in the earth's crust is 2.4 percent. The most common minerals containing potassium are salvinite and carnallite. The first has the following chemical formula: NaCl.KCl. It has a variegated color and consists of many crystals of various colors. Depending on the ratio of potassium chloride and sodium, as well as the presence of impurities, it may contain red, blue, pink, and orange components. The second mineral - carnallite - looks like transparent, soft blue, light pink or pale yellow crystals. Its chemical formula looks like this: KCl.MgCl2.6H2O. It is a crystalline hydrate.
The role of potassium in the body, symptoms of deficiency and excess
It, together with sodium, maintains the water-salt balance of the cell. It is also involved in the transmission of nerve impulses between membranes. In addition, it regulates the acid-base balance in the cell and throughout the body as a whole. It takes part in metabolic processes, counteracts the occurrence of edema, and is part of the cytoplasm - about fifty percent of it - the salt of the metal in question. The main signs that the body does not have enough potassium are swelling, the occurrence of a disease such as dropsy, irritability and disturbances in the functioning of the nervous system, slow reaction and memory impairment.
In addition, an insufficient amount of this microelement negatively affects the cardiovascular and muscular systems. A lack of potassium over a very long period of time can cause a heart attack or stroke. But due to excess potassium in the body, a small intestinal ulcer can develop. To balance your diet so that you get the normal amount of potassium, you need to know what foods contain it.
Foods high in the micronutrient in question
First of all, these are nuts such as cashews, walnuts, hazelnuts, peanuts, almonds. Also, a large amount of it is found in potatoes. In addition, potassium is found in dried fruits such as raisins, dried apricots, and prunes. Pine nuts are also rich in this element. Its high concentration is also observed in legumes: beans, peas, lentils. Sea kale is also rich in this chemical element. Other products that contain this element in large quantities are green tea and cocoa. In addition, it is found in high concentrations in many fruits, such as avocados, bananas, peaches, oranges, grapefruits, and apples. Many cereals are rich in this microelement. This is primarily pearl barley, as well as wheat and buckwheat. Parsley and Brussels sprouts also have a lot of potassium. In addition, it is found in carrots and melon. Onions and garlic contain a considerable amount of the chemical element in question. Chicken eggs, milk and cheese are also high in potassium. The daily norm of this chemical element for the average person is from three to five grams.
Conclusion
After reading this article, we can conclude that potassium is an extremely important chemical element. It is necessary for the synthesis of many compounds in the chemical industry. In addition, it is used in many other industries. It is also very important for the human body, so it must be supplied there regularly and in the required quantity with food.
There are three main classes of compounds. These are acids, alkalis and oxides. An acid consists of a hydrogen cation and an acidic anion. Alkali - made from a metal cation and a hydroxyl group. We will talk about oxides in more detail later.
What is an oxide?
This is a compound consisting of two different chemical elements, one of which is oxygen. The second one can be metal or non-metal. The number of oxygen atoms depends on the valence of the second chemical element included in the compound. So, for example, the valence of potassium is one, so potassium oxide will contain one oxygen atom and two potassium atoms. The valency of calcium is two, so its oxide will consist of one oxygen atom and one calcium atom. The valency of phosphorus is five, so its oxide consists of two phosphorus atoms and five oxygen atoms.
In this article we will talk in more detail about potassium oxide. Namely - about its physical and chemical properties, about its application in various fields of industry.
Potassium oxide: formula
Since the valency of this metal is one, and the valence of oxygen is two, this chemical compound will consist of two metal atoms and one oxygen atom. So, potassium oxide: formula - K 2 O.
Physical properties
The oxide in question has a pale yellow color. Sometimes it can be colorless. At room temperature it has a solid state of aggregation.
The melting point of this substance is 740 degrees Celsius.
The density is 2.32 g/cm3.
The thermal decomposition of this oxide produces peroxide of the same metal and pure potassium.
Soluble in organic solvents.
It does not dissolve in water, but reacts with it.
It is highly hygroscopic.
Chemical properties of K 2 O
This substance has chemical properties typical of all basic oxides. Let us consider the chemical reactions of this oxide with various substances in order.
Reaction with water
First of all, it is capable of reacting with water to form the hydroxide of this metal.
The equation for such a reaction is as follows:
- K 2 O + H 2 O = 2 KON
Knowing the molar mass of each substance, the following conclusion can be drawn from the equation: from 94 grams of the oxide in question and 18 grams of water, 112 grams of potassium hydroxide can be obtained.
With other oxides
In addition, the oxide in question is capable of reacting with carbon dioxide (carbon dioxide). In this case, a salt is formed - potassium carbonate.
The reaction equation for potassium oxide and carbon oxide can be written as follows:
- K 2 O + CO 2 = K 2 CO 3
So, we can conclude that from 94 grams of the oxide in question and 44 grams of carbon dioxide, 138 grams of potassium carbonate are obtained.
Also, the oxide in question can react with sulfur oxide. In this case, another salt is formed - potassium sulfate.
The interaction of potassium oxide with sulfur oxide can be expressed by the following equation:
- K 2 O + SO 3 = K 2 SO 4
It shows that by taking 94 grams of the oxide in question and 80 grams of sulfur oxide, you can get 174 grams of potassium sulfate.
In the same way, K 2 O can react with other oxides.
Another type of interaction is reactions not with acidic, but with amphoteric oxides. In this case, it is not an acid that is formed, but a salt. An example of such a chemical process is the interaction of the oxide in question with zinc oxide.
This reaction can be expressed by the following equation:
- K 2 O + ZnO = K 2 ZnO 2
It shows that when the oxide in question interacts with zinc oxide, a salt called potassium zincate is formed. If you know the molar mass of all substances, then you can calculate that from 94 grams of K 2 O and 81 grams of zinc oxide you can get 175 grams of potassium zincate.
K2O is also capable of interacting with nitric oxide. In this case, a mixture of two salts is formed: potassium nitrate and nitrite. The equation for this reaction looks like this:
- K 2 O + 2NO 2 = KNO 3 + KNO 2
If you know the molar masses of substances, we can say that from 94 grams of the oxide in question and 92 grams of nitrogen oxide, you can get 101 grams of nitrate and 85 grams of nitrite.
Interaction with acids
The most common case is potassium oxide + sulfuric acid = potassium sulfate + water. The reaction equation looks like this:
- K 2 O + H 2 SO 4 = K 2 SO 4 + H 2 O
From the equation we can conclude that to obtain 174 grams of potassium sulfate and 18 grams of water, it is necessary to take 94 grams of the oxide in question and 98 grams of sulfuric acid.
In a similar way, a chemical interaction occurs between the oxide in question and nitric acid. This produces potassium nitrate and water. The equation for this reaction can be written as follows:
- 2K 2 O + 4HNO 3 = 4KNO 3 + 2H 2 O
Thus, from 188 grams of the oxide in question and 252 grams of nitric acid, 404 grams of potassium nitrate and 36 grams of water can be obtained.
By the same principle, the oxide in question can react with other acids. During this process, other salts and water will be formed. So, for example, when this oxide reacts with phosphoric acid, phosphate and water are obtained, with chloride acid - chloride and water, and so on.
K 2 O and halogens
The chemical compound in question is capable of reacting with substances of this group. Halogens are simple compounds consisting of several atoms of the same chemical element. These are, for example, chlorine, bromine, iodine and some others.
So, chlorine and potassium oxide: equation:
- K 2 O + CI 2 = KSI + KSIO
As a result of this interaction, two salts are formed: potassium chloride and potassium hypochlorite. From 94 grams of the oxide in question and 70 grams of chlorine, 74 grams of potassium chloride and 90 grams of potassium hypochlorite are obtained.
Interaction with ammonia
K 2 O is able to react with this substance. As a result of this chemical interaction, potassium hydroxide and amide are formed. The equation for this reaction is as follows:
- K 2 O + NH 3 = KOH + KNH 2
Knowing the molar masses of all substances, you can calculate the proportions of reactants and reaction products. From 94 grams of the oxide in question and 17 grams of ammonia, you can get 56 grams of potassium hydroxide and 55 grams of potassium amide.
Interaction with organic substances
Among organic chemicals, potassium oxide reacts with ethers and alcohols. However, these reactions are slow and require special conditions.
Obtaining K 2 O
This chemical can be obtained in several ways. Here are the most common ones:
- From potassium nitrate and potassium metal. These two reactants are heated, resulting in the formation of K 2 O and nitrogen. The reaction equation is as follows: 2KNO 3 + 10K = N 2 + 6K 2 O.
- The second method occurs in two stages. First, a reaction occurs between potassium and oxygen, resulting in the formation of potassium peroxide. The reaction equation looks like this: 2K + O 2 = K 2 O 2. Next, the peroxide is enriched with potassium, resulting in potassium oxide. The reaction equation can be written as follows: K 2 O 2 + 2K = 2K 2 O.
Use of K2O in industry
The most commonly used substance in question is in the agricultural industry. This oxide is one of the components of mineral fertilizers. Potassium is very important for plants, as it increases their resistance to various diseases. The substance in question is also used in construction, as it may be present in some types of cement. In addition, it is used in the chemical industry to produce other potassium compounds.
