Potassium is the nineteenth element of the periodic table and belongs to the alkali metals. This is a simple substance that, under normal conditions, resides 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.
He 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.
Such interaction is considered qualitative reaction for potassium determination. Reactions of potassium with halogens are named according to their names chemical elements: this is fluoridation, 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 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 of Mendeleev 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: from atomic mass subtract the serial number of a chemical element. Conclusion: there are 20 protons in the potassium nucleus. Potassium belongs to the IV period, has 4 “orbits”, on which electrons are evenly located, staying in constant movement. The first “orbit” contains 2 electrons, the second - 8; in the third and last, fourth “orbit”, 1 electron rotates. This explains high level 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 discuss and electronic formula potassium, and its behavior with other substances, etc. It 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 from the point of view 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 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 surrounding 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. The result is two moles of potassium compound. This reaction is expressed by the following equation: 2К + СІ2 = 2КІ. Potassium can form compounds with nitrogen 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 appears as green-black crystals. The metal in question reacts with phosphorus 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 can react with hydrogen to form 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
With this group inorganic substances the metal in question reacts only when heated significantly. 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. Express this process using the equation you can do it as follows: 3К + 2АІСІ3 = 3КСІ2 + 2АІ.
Reactions with fats
If you add potassium to any organic matter 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 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. His 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 diseases such as dropsy, irritability and disturbances in work 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.
Task No. 1.
In the picture shown
depicts a model of an atom
1. Silicon
2. Sulfur
3. Oxygen
4. Carbon
Explanation: the atom, the model of which is shown in the figure, has two energy levels, the first level has 2 electrons, and the second has 4. This means that this is an atom of element No. 6 in the Periodic Table - carbon. The correct answer is 4.
Task No. 2.
For chemical elements of group IVA of the periodic system with increasing relative atomic mass:
1. Metallic properties are enhanced and valence in hydrogen compounds increases
2. The charge of the atomic nucleus and the radius of the atom increase
3. The number of electronic layers in an atom and the highest valency increase
4. Non-metallic properties increase and the number of electronic layers in an atom increases
Explanation: Elements of the same group have valency in hydrogen compounds and the highest valency. And the charge of the atomic nucleus and the radius of the atom in the group increase. For example, carbon has a nuclear charge of +6, and silicon has a +14. The correct answer is 2.
Task No. 3.
Compounds with covalent polar and covalent nonpolar bonds are, respectively:
1. Chlorine and hydrogen chloride
2. Water and nitrogen
3. Hydrogen sulfide and methane
4. Oxygen and sulfur oxide (IV)
Explanation: covalent polar connection is characteristic of compounds of various non-metals, and a covalent non-polar bond is characteristic of diatomic non-metals, so we choose water and nitrogen. The correct answer is 2.
Task No. 4.
In substances whose formulas are: CrO3, CrCl2, Cr(OH)3, chromium exhibits oxidation states correspondingly equal to:
1. +6, +2, +3
2. +6, +3, +2
3. +3, +2, +3
4. +3, +2, +6
Explanation: CrO3 - oxygen in oxides has an oxidation state of -2, then for chromium it is +6, CrCl2 - for chlorine the oxidation state is -1, and for chromium it is +2, Cr(OH)3 - for the hydroxide ion the oxidation state is -1 , and for chromium - +3. The correct answer is 1.
Task No. 5.
Complex substances include each of the substances indicated in the series
1. Carbon dioxide, water, nitrogen, chlorine
2. Table salt, sugar, hydrogen chloride, ammonia
3. Hydrogen sulfide, calcium, chlorine, methane
4. Sulfuric acid, fluorine, zinc oxide, aluminum
Explanation: complex substances consist of atoms of two or more elements, these include: table salt, sugar, hydrogen chloride, ammonia. The correct answer is 2.
Task No. 6.
Gas formation occurs when solutions are drained:
1. Calcium chloride and silver nitrate
2. Nitric acid and potassium hydroxide
3. Sodium carbonate and hydrochloric acid
4. Iron (III) hydroxide and sulfuric acid
Explanation: gas evolution is possible with the formation of carbonic or sulfurous acid or ammonium hydroxide; carbonic acid is formed in the third reaction. Let's write it down:
Na2CO3 + 2HCl = 2NaCl + CO2 + H2O
The correct answer is 3.
Task No. 7.
Electrolytes include each of the substances whose formulas are:
1. N2O, KOH, Na2CO3
2. Cu(NO3)2, HCl, Na2SO4
3. Ba(OH)2, NH3xH2O, H2SiO3
4. CaCl2, Cu(OH)2, SO2
Explanation: electrolyte - a conductive substance electricity upon dissociation into ions. Strong electrolytes are alkalis, strong acids and salt. The correct answer is 2.
Task No. 8.
According to the reduced ionic equation
Al³ + + 3OH‾ = Al(OH)3
interacts:
1. Aluminum sulfate and barium hydroxide
2. Aluminum nitrate and potassium hydroxide
3. Aluminum oxide and sodium hydroxide
4. Aluminum phosphate and calcium hydroxide
Explanation: This abbreviated ionic equation can only be obtained in a reaction in which the only insoluble substance is aluminum hydroxide. In the first reaction, barium sulfate is insoluble, in the third - aluminum oxide, in the fourth - calcium phosphate. All nitrates and all potassium salts are soluble, so we choose the second equation. The correct answer is 2.
Task No. 9.
Iron displaces metal from solution:
1. ZnCl2
2. Cu(NO3)2
3. Al2(SO4)3
4. Mg(NO3)2
Explanation: iron can only displace a weaker metal; among those listed, only copper is a weaker metal. The correct answer is 2.
Task No. 10.
Potassium oxide reacts with each of the substances indicated in the series
1. Water, carbon monoxide (II), sulfuric acid
2. Barium oxide, water, sodium hydroxide
3. Water, carbon monoxide (IV), hydrochloric acid
4. Ammonia, oxygen, nitric acid
Explanation: Barium oxide is a basic oxide, that is, it reacts with substances with acidic properties, such as carbon monoxide (IV) and hydrochloric acid, and with water to form potassium hydroxide. The correct answer is 3.
Task No. 11.
Insoluble salt is formed when solutions interact
1. Sodium chloride and nitric acid
2. Magnesium chloride and sodium carbonate
3. Copper(II) chloride and sodium hydroxide
4. Aluminum chloride and sulfuric acid
Explanation: in the first reaction a soluble salt is formed - sodium nitrate, in the second - magnesium carbonate (insoluble) and sodium chloride (soluble). In the third - soluble sodium chloride, in the fourth - soluble aluminum sulfate. The correct answer is 2.
Task No. 12.
Potassium phosphate solution reacts
1. With calcium nitrate
2. With nitric acid
3. With ammonium sulfate
4. With sodium hydroxide
Explanation: here an exchange reaction must take place; it goes to completion only if a precipitate or gas is formed. In the first reaction, potassium nitrate (all nitrates are soluble) and calcium phosphate (precipitate) are formed, which means the reaction proceeds to completion. The correct answer is 1.
Task No. 13.
When mixed with air, each of the gases becomes explosive:
1. Nitric oxide (II) and methane
2. Hydrogen and carbon monoxide (II)
3. Sulfur (IV) oxide and ammonia
4. Methane and hydrogen
Explanation: air contains oxygen; when oxygen and hydrogen are mixed in a certain volume, an explosive reaction occurs, and methane is a very energy-intensive gas and burns in air, releasing large quantity heat. The correct answer is 4.
Task No. 14.
Sulfur is the oxidizing agent in the reaction, the equation of which is:
1. 2SO2 + O2 = 2SO3
2. 2H2S + 3O2 = 2H2O + 2SO2
3. H2S + Br2 = 2HBr + S
4. 2Al + 3S = Al2S3
Explanation: The oxidizing agent accepts electrons in a redox reaction. Let us consider changes in the oxidation states of sulfur in the given reactions.
1. +4 (-2e) → +6
2. -2 (-6e) → +4
3. -2 (-2e) → 0
4. 0 (+2e) → -2
That is, sulfur accepts electrons in the last reaction. The correct answer is 4.
Task No. 15.
The mass fraction of calcium in calcium carbonate is equal to:
1. 0,8
2. 0,4
3. 0,2
4. 0,6
Explanation: Let's calculate the mass fraction of calcium using the formula:
ω = (Ar(Ca) x n)/Mr, where n is the number of calcium atoms in the molecule.
ω(Ca) = 40/100 = 0.4
The correct answer is 2.
Task No. 16.
What magnesium and zinc have in common is
1. Availability the same number electron layers in their atoms
2. The presence of two electrons on the outer electron layer in their atoms
3. Their formation of higher oxides, which are classified as basic oxides
4. The fact that they are reducing agents in reactions with non-metals
5. The fact that their oxides are highly soluble in water
Explanation: magnesium is in the third period, in the second A group and is an alkaline earth metal, zinc is in the fourth period, in the second B group and is a transition metal, that is, these two elements have a different number of electronic layers. But the number of electrons at the external level is the same - 2. Zinc oxide is amphoteric, not basic. And in reactions with non-metals they are reducing agents, as they donate electrons. Their oxides do not dissolve in water. The correct answer is 24.
Task No. 17.
The following statements are typical for ethane
1. Discolors bromine water
2. Enters into a dehydrogenation reaction
3. Carbon atoms in a molecule are connected by single bonds
4. The molecule contains one carbon atom
5. Refers to oxygen-containing organic substances
Explanation: ethane is a saturated hydrocarbon, that is, it is characterized mainly by substitution reactions. It can also dehydrogenate, turning into ethylene or acetylene. The correct answer is 23.
Task No. 18.
Establish a correspondence between two substances and a reagent that can be used to distinguish between these substances
Substances
1. SO3(g) and O2(g)
2. HNO3(solution) and NH3(solution)
3. BaCO3(s) and BaO(s)
Reagent
1. Na2SO4(solution)
2. Ca(OH)2(solution)
3. Phenolphthalein
4. HCl(solution)
Explanation: the first two gases can be distinguished in the reaction with calcium hydroxide: sulfur oxide will form a salt - calcium sulfate, but oxygen will not react. Solutions of nitric acid and ammonia can be distinguished using an indicator - phenolphthalein; it will give different colors: in an acidic environment it will be colorless, and in a slightly alkaline environment it will be pink. The correct answer is 234.
Task No. 19.
Match the name of a substance with the reagents with which this substance can interact
Substance name
A. Hydrogen sulfide
B. Sulfur (VI) oxide
B. Sulfur (IV) oxide
Reagents
1. O2, KOH(solution)
2. Hg, H2O
3. O2, Cu
4. H2O, CaO
Explanation: Hydrogen sulfide reacts with oxygen (with a lack of oxygen, sulfur and water are formed, and with an excess of oxygen, sulfur oxide (IV) is formed) and with potassium hydroxide (with the formation of potassium sulfide and water). Sulfur (IV) oxide reacts with the same reagents. And sulfur oxide (VI) reacts with water to form sulfuric acid and with calcium oxide to form calcium sulfate. The correct answer is 141.
Task No. 20.
Using the electronic balance method, arrange the coefficients in the reaction equation, the diagram of which
K2MnO4 + HCl(conc) → MnCl2 + KCl + Cl2 + H2O
Identify the oxidizing agent and the reducing agent.
Explanation: In this reaction, the oxidation state is changed - manganese and chlorine.
Let's write down the balance:
Mn(+6) +4e → Mn(+2) | 1 - oxidizing agent
2Cl(-1) -2e → Cl2(0) | 2 - reducing agent
Let's arrange the coefficients.
K2MnO4 + 8HCl(conc) → MnCl2 + 2KCl + 2Cl2 + 4H2O
Task No. 21.
An excess of sulfuric acid solution was added to 400 g of potassium silicate solution and 19.5 g of precipitate was obtained. What is mass fraction salts (in%) in the original solution?
Explanation: Let's write down the reaction.
K2SiO3 + H2SO4 → H2SiO3↓ + K2SO4
Let's calculate the amount of silicic acid substance.
n(H2SiO3) = 19.5/(2+28+48) = 0.25 mol
n(H2SiO3) = n(K2SiO3) = 0.25 mol
Let's calculate the mass of the potassium silicate substance.
M(K2SiO3) = 39x2 + 28 + 48 = 154 g/mol
m(K2SiO3) = 0.25 x 154 = 38.5 g
ω(K2SiO3) = 38.5/400 x 100% = 9.625%
Answer: the mass fraction of salt in the original solution is 9.625%.
Task No. 22.
Given substances: ZnSO4, HNO3(conc), Hg, Cu, I2, KOH. Using water and necessary substances only from this list, obtain copper (II) hydroxide in two stages. Describe the signs of reactions. For an ion exchange reaction, write the abbreviated ionic equation for the reaction.
Explanation: Let's say copper reacts with concentrated nitric acid.
Cu + 4HNO3(conc) = Cu(NO3)2 + 2NO2 + 2H2O
And then copper nitrate will react with potassium hydroxide, forming insoluble copper hydroxide.
Cu(NO3)2 + KOH = KNO3 + Cu(OH)2↓
Potassium oxide is a solid crystalline substance that forms colorless crystals. It has two stable crystalline modifications: cubic (up to 372°C) and hexagonal (above 372°C).
- Melting point - 740°C.
- Density - 2.32 g/cm3.
Potassium oxide melts in air and, absorbing CO 2, gives K 2 CO 3. It reacts violently with water to form KOH. Reacts with ether and alcohol.
At a temperature of 250°C it reacts with H2. In this case, KOH is formed. At the same temperature, it reacts with NH 3, forming KOH and KNH 2.
Three-dimensional model of a molecule
It energetically reacts with halogens, molten acids, and various acids. When heated with oxides of boron, aluminum, and silicon, it forms borates, aluminates, and polysilicates, respectively.
When heated with NO 2, a mixture of KNO 3 and KNO 2 is formed.
Potassium oxide is obtained:
Potassium oxide content in soil and fertilizers
The availability of potassium to plants depends on the form of potassium availability in the soil. PPC cations and water-soluble potassium compounds are the main sources of potassium nutrition for plants. In this regard, the degree of potassium supply to the soil for plant nutrition is expressed by the content in mobile form and through potassium oxide K 2 O. This value denotes the total amount of exchangeable and water-soluble calcium in mg/kg of soil.
Potash fertilizers are highly soluble in water. When introduced into the soil, they quickly dissolve and, based on metabolic reactions, interact with PPC. Part of the potassium in fertilizers goes into non-exchangeable fixed soil compounds.