Which metal does not dissolve in water?

Water as a solvent - properties, meaning and examples

Water as a solvent plays an extremely important role not only in terms of our everyday life. Researchers have long said that this magical compound is the basis for the formation of life in general. And that is why its presence is a prerequisite for the existence of something more complex than inanimate nature.

The solubility of certain chemical elements is directly related to the existence of water, since it most often acts as the medium that transforms everything around it and creates new forms of organic and inorganic matter. 

A person is approximately 70% water (meaning blood, intercellular fluid, blood plasma and other substances), for most other creatures this figure ranges from 50 to 95%. It is obvious that the properties of this compound have a decisive role on the processes of synthesis, regeneration and many others occurring around us and within us.  

This is a universal solvent that literally shapes the world around us, constantly transforms and renews it!

Properties of water as a solvent

Water is a complex substance with many unique characteristics that cannot be found anywhere else. 

It is capable of dissolving most of the complex compounds existing in nature, containing in their structure molecules with both positive and negative ions at the same time. 

When conducting so-called kinetic studies, all solutions are also prepared on the basis of H2O.

A striking example of the peculiarity of water - although its structure is similar to methane CH 4 , it has a boiling point higher by as much as 250 C! 

An important role is also played by its ability to act simultaneously as either a donor or an acceptor of hydrogen particles, due to which many chemical processes take place. Chemistry also tells us that water is an ideal solvent for dissociating compounds.  

It is interesting to note that due to the high level of dielectric constant, water perfectly shields the electric fields of ions from each other. Due to this, the attraction of oppositely charged particles in water is reduced by about 80 times.

What substances dissolve in water

Even if a student only goes to 3rd grade, he can probably give examples of materials that are afraid of contact with water, or, in other words, dissolve in it and lose their properties. 

Here is a list of just some substances of this type:

1. Well-soluble ones include: salt, sugar, soda, chlorides, alkali metals and nitrates, as well as bromides. Air also undergoes changes when in contact with a liquid medium. Starch is completely soluble, as is alcohol.

2. The average degree of interaction includes: Berthollet salt, methane, gypsum, oxygen, nitrogen, other chemical elements, for example, sulfates, some gaseous substances.

3. There are also materials that are insoluble: copper sulfide, glass, gold, kerosene, silver, vegetable fat and many others. True, under some conditions even they are not able to resist such a powerful influence.

The human body has a whole group of vitamins (C, B1, 2, 3 (PP), B12 and others), which are able to exert their positive effects on health only in contact with H2O. This also applies to folic acid, biotin, etc.

What does not dissolve in water

There are chemical formations that do not perceive the effects of water as a solvent at all. 

A good example: carbon C, which is found in a simple pencil, many metals and alloys, such as aluminum, as well as gold, silver, copper. 

This situation arises due to the fact that there are strong bonds between the molecules and atoms of insoluble substances, which hydrogen is not able to destroy. The polar state of the molecule also contributes to the greater strength of the material that consists of such particles.

Many things that we see around us in everyday life are also insoluble. A very popular example is plastic. 

There is a huge patch of plastic debris floating in the world's oceans, which is growing every year, and the amount of plastic there does not want to decrease naturally. It cannot be processed in any way, which is very bad for the entire ecosystem.  

That is why environmentalists are sounding the alarm and the EU is already planning to abandon plastic bags, plastic cups and straws, and similar measures.

The importance of water as a solvent

As already mentioned at the beginning of the article, the properties of water under consideration are key for all living and inanimate nature of our planet. 

If it did not have these characteristics, then most chemical processes on Earth, in living organisms, in organic nature would simply stop. The picture of such a world would be very disappointing - a dark desert with no signs of life.

The role of water is so enormous that its determination in distant planets and galaxies is the main activity for astronomers in the hope of one day finding there, if not intelligent existence, then at least the beginnings of life.

Source: https://nauka.club/khimiya/voda-kak-rastvoritel.html

Chemical and physical properties of iron, application:

Iron is considered one of the most common metals in the earth's crust after aluminum. Its physical and chemical properties are such that it has excellent electrical conductivity, thermal conductivity and malleability, has a silver-white color and high chemical reactivity to quickly corrode at high humidity or high temperatures. Being in a finely dispersed state, it burns in pure oxygen and spontaneously ignites in air.

The beginning of the history of iron

In the third millennium BC. e. people began to mine and learned to process bronze and copper. They were not widely used due to their high cost. The search for new metal continued. The history of iron began in the first century BC. e. In nature, it can only be found in the form of compounds with oxygen. To obtain pure metal, it is necessary to separate the last element.

It took a long time to melt the iron, since it had to be heated to 1539 degrees. And only with the advent of cheese-making furnaces in the first millennium BC did they begin to obtain this metal. At first it was fragile and contained a lot of waste. With the advent of forges, the quality of iron improved significantly. It was further processed in a blacksmith, where the slag was separated by hammer blows.

Forging has become one of the main types of metal processing, and blacksmithing has become an indispensable branch of production. Iron in its pure form is a very soft metal. It is mainly used in an alloy with carbon. This additive enhances the physical property of iron, such as hardness. The cheap material soon penetrated widely into all spheres of human activity and revolutionized the development of society.

After all, even in ancient times, iron products were covered with a thick layer of gold. It had a high price compared to the noble metal.

Iron in nature

The lithosphere contains more aluminum than iron. In nature, it can only be found in the form of compounds. Ferric iron, reacting, turns the soil brown and gives the sand a yellowish tint. Iron oxides and sulfides are scattered in the earth's crust, sometimes there are accumulations of minerals, from which the metal is subsequently extracted.

Ferrous iron in some mineral springs gives the water a special taste. Rusty water flowing from old water pipes is colored by the trivalent metal. Its atoms are also found in the human body. They are found in hemoglobin (iron-containing protein) in the blood, which supplies the body with oxygen and removes carbon dioxide.

Some meteorites contain pure iron, sometimes whole ingots are found.

What physical properties does iron have?

It is a ductile silver-white metal with a grayish tint and a metallic sheen. It is a good conductor of electric current and heat. Due to its ductility, it lends itself perfectly to forging and rolling.

Iron does not dissolve in water, but liquefies in mercury, melts at a temperature of 1539 and boils at 2862 degrees Celsius, and has a density of 7.9 g/cm³.

A peculiarity of the physical properties of iron is that the metal is attracted by a magnet and, after the cancellation of the external magnetic field, retains magnetization. Using these properties, it can be used to make magnets.

Chemical properties

Iron has the following properties:

• in air and water it easily oxidizes, becoming covered with rust;
• in oxygen, the hot wire burns (and scale is formed in the form of iron oxide);
• at a temperature of 700–900 degrees Celsius, it reacts with water vapor;
• when heated, reacts with non-metals (chlorine, sulfur, bromine);
• reacts with dilute acids, resulting in iron salts and hydrogen;
• does not dissolve in alkalis;
• is capable of displacing metals from solutions of their salts (an iron nail in a solution of copper sulfate becomes covered with a red coating - this is the release of copper);
• In concentrated alkalis when boiling, the amphotericity of iron is manifested.

Feature properties

One of the physical properties of iron is ferromagneticity. In practice, the magnetic properties of this material are often encountered. This is the only metal that has such a rare feature.

Under the influence of a magnetic field, iron is magnetized. The metal retains its formed magnetic properties for a long time and remains a magnet itself.

This exceptional phenomenon is explained by the fact that the structure of iron contains a large number of free electrons that can move.

Reserves and production

One of the most common elements on earth is iron. In terms of content in the earth's crust, it ranks fourth. There are many known ores that contain it, for example, magnetic and brown iron ore. The metal is produced in industry mainly from hematite and magnetite ores using the blast furnace process. First, it is reduced with carbon in a furnace at a high temperature of 2000 degrees Celsius.

To do this, iron ore, coke and flux are fed into the blast furnace from above, and a stream of hot air is injected from below. A direct process for obtaining iron is also used. The crushed ore is mixed with special clay to form pellets. Next, they are fired and treated with hydrogen in a shaft furnace, where it is easily restored. They obtain solid iron and then melt it in electric furnaces.

Pure metal is reduced from oxides using electrolysis of aqueous salt solutions.

Benefits of Iron

The basic physical properties of the iron substance give it and its alloys the following advantages over other metals:

• They have hardness and strength while maintaining elasticity. These qualities are not the same for different alloys and depend on alloying additives, production methods and heat treatment.
• A wide variety of cast iron and steels allow them to be used for any needs in the national economy.
• The high magnetic properties of metal are indispensable for the manufacture of magnetic cores.
• The feasibility of light mechanical processing, due to the physical properties of iron, makes it possible to obtain sheets, rods, beams, pipes, and shaped profiles from its alloys.
• The significant malleability of the material allows it to be used for decorative products.
• Low cost of alloys.

Flaws

In addition to a large number of positive qualities, there are also a number of negative properties of the metal:

• Products are susceptible to corrosion. To eliminate this undesirable effect, stainless steels are produced by alloying, and in other cases, special anti-corrosion treatment is carried out on structures and parts.
• Iron accumulates static electricity, so products containing it are subject to electrochemical corrosion and also require additional processing.
• The specific gravity of the metal is 7.13 g/cm³. This physical property of iron gives structures and parts increased weight.

Composition and structure

Iron has four crystalline modifications that differ in structure and lattice parameters. For the smelting of alloys, it is the presence of phase transitions and alloying additives that is of significant importance. The following states are distinguished:

• Alpha phase. It lasts up to 769 degrees Celsius. In this state, iron retains the properties of a ferromagnet and has a body-centered cubic lattice.
• Beta phase. Exists at temperatures from 769 to 917 degrees Celsius. It has slightly different lattice parameters than in the first case. All physical properties of iron remain the same, with the exception of magnetic ones, which it loses.
• Gamma phase. The lattice structure becomes face-centered. This phase appears in the range of 917–1394 degrees Celsius.
• Omega phase. This state of the metal appears at temperatures above 1394 degrees Celsius. It differs from the previous one only in the lattice parameters.

Iron is the most sought after metal in the world. More than 90 percent of all metallurgical production falls on it.

Application

People first began to use meteorite iron, which was valued higher than gold. Since then, the scope of this metal has only expanded. The following are the uses of iron based on its physical properties:

• ferromagnetic oxides are used for the production of magnetic materials: industrial installations, refrigerators, souvenirs;
• iron oxides are used as mineral paints;
• ferric chloride is indispensable in amateur radio practice;
• Ferrous sulfates are used in the textile industry;
• magnetic iron oxide is one of the important materials for the production of long-term computer memory devices;
• ultrafine iron powder is used in black and white laser printers;
• the strength of the metal makes it possible to manufacture weapons and armor;
• wear-resistant cast iron can be used to produce brakes, clutch discs, and parts for pumps;
• heat-resistant – for blast furnaces, thermal furnaces, open-hearth furnaces;
• heat-resistant – for compressor equipment, diesel engines;
• high-quality steel is used for gas pipelines, casings of heating boilers, dryers, washing machines and dishwashers.

Conclusion

Iron often means not the metal itself, but its alloy - low-carbon electrical steel. Obtaining pure iron is a rather complex process, and therefore it is used only for the production of magnetic materials. As already noted, the exclusive physical property of the simple substance iron is ferromagnetism, i.e.

the ability to be magnetized in the presence of a magnetic field. The magnetic properties of pure metal are up to 200 times higher than those of technical steel. This property is also affected by the grain size of the metal. The larger the grain, the higher the magnetic properties. Mechanical processing also has an effect to some extent.

Such pure iron that meets these requirements is used to produce magnetic materials.

Source: https://www.syl.ru/article/369165/himicheskie-i-fizicheskie-svoystva-jeleza-primenenie

Solubility of copper in water: does it dissolve and why?

› About water ›

When studying all chemical elements, special attention is paid to their ability to dissolve in water. Since the solubility of copper in water is low, the corrosion process is practically not observed, and due to the special chemical properties of the metal, compounds with other elements are used in a wide variety of industries.

Basic properties

Copper is a metal with a pink or reddish tint. The radius of its positively charged ions is characterized by the following values:

• with a coordination index of 6 – up to 0.091 nm;
• with a coordination index of 2 – up to 0.06 nm.

An atom of this element has a radius size of 0.128 nm, which corresponds to an electron of 1.8 eV. Since copper is a transition metal, its electronegativity, according to the Pauling scale, is 1.9. In addition, this element is characterized by different oxidation states.

The physical properties of copper also include thermal conductivity, which at a temperature of 20-100°C corresponds to 394 W/m*K. As for electrical conductivity, it is 55.5-58 MSm. This metal is not capable of displacing hydrogen from acids and water. The size of its face-centered cubic crystal lattice is 0.36150 nm. A temperature of 1082°C determines the melting process of this chemical element, and 26570 determines the process of its boiling.

Solubility in water

Solubility is the ability to form homogeneous mixtures or solutions during the interaction of a compound with another substance. Their components are individual particles - atoms, molecules, ions. The concentration of a substance indicates its level of solubility in another substance. It is usually expressed as a percentage, weight or volume fraction.

Many people are interested in whether copper dissolves in water. As with other solid compounds, this process is determined only by temperature changes. The dependence is calculated using the curve method. At a very low value (that is, a low concentration of the substance in the solvent), the substance is considered to be insoluble. The action of sea water does not cause corrosion of copper, which is proof of its inertness under normal conditions.

Copper is practically insoluble in fresh water. However, a humid environment and the influence of carbon dioxide contribute to the formation of a green film on the metal. If we talk about its monovalent compounds, in particular salts, they are slightly soluble.

These substances quickly oxidize and eventually form divalent compounds. It is these salts that have the ability to dissolve in water. As a result of dissociation, they completely disintegrate into ions.

Source: https://vseowode.ru/prosto-o-vode/rastvorimost-v-vode-medi.html

Aluminum corrosion

Aluminum corrosion is the destruction of metal under the influence of the environment.

For the reaction Al3+ +3e → Al, the standard electrode potential of aluminum is -1.66 V.

The melting point of aluminum is 660 °C.

The density of aluminum is 2.6989 g/cm3 (under normal conditions).

Aluminum, although an active metal, has fairly good corrosion properties. This can be explained by the ability to passivate in many aggressive environments.

The corrosion resistance of aluminum depends on many factors: the purity of the metal, the corrosive environment, the concentration of aggressive impurities in the environment, temperature, etc. The pH of solutions has a strong influence. Aluminum oxide forms on the metal surface only in the pH range from 3 to 9!

The corrosion resistance of Al is greatly influenced by its purity. For the manufacture of chemical units and equipment, only high-purity metal (without impurities), for example, AB1 and AB2 aluminum, is used.

Corrosion of aluminum is not observed only in those environments where a protective oxide film is formed on the surface of the metal.

When heated, aluminum can react with some non-metals:

2Al + N2 → 2AlN – interaction of aluminum and nitrogen with the formation of aluminum nitride;

 4Al + 3С → Al4С3 – reaction of interaction of aluminum with carbon with the formation of aluminum carbide;

2Al + 3S → Al2S3 – interaction of aluminum and sulfur with the formation of aluminum sulfide.

Corrosion of aluminum in air (atmospheric corrosion of aluminum)

Aluminum, when interacting with air, becomes passive. When pure metal comes into contact with air, a thin protective film of aluminum oxide instantly appears on the aluminum surface. Further, film growth slows down. The formula of aluminum oxide is Al2O3 or Al2O3•H2O.

The reaction of aluminum with oxygen:

4Al + 3O2 → 2Al2O3.

 The thickness of this oxide film ranges from 5 to 100 nm (depending on operating conditions). Aluminum oxide has good adhesion to the surface and satisfies the condition of continuity of oxide films. When stored in a warehouse, the thickness of aluminum oxide on the metal surface is about 0.01 - 0.02 microns. When interacting with dry oxygen – 0.02 – 0.04 microns. When heat treating aluminum, the thickness of the oxide film can reach 0.1 microns.

Aluminum is quite resistant both in clean rural air and in an industrial atmosphere (containing sulfur vapor, hydrogen sulfide, ammonia gas, dry hydrogen chloride, etc.). Because sulfur compounds do not have any effect on the corrosion of aluminum in gas environments - it is used for the manufacture of sour crude oil processing plants and rubber vulcanization devices.

Corrosion of aluminum in water

Aluminum corrosion is almost not observed when interacting with clean, fresh, distilled water. Increasing the temperature to 180 °C does not have any special effect. Hot water vapor also has no effect on aluminum corrosion. If you add a little alkali to water, even at room temperature, the corrosion rate of aluminum in such an environment will increase slightly.

https://www.youtube.com/watch?v=fFuA8XC8tIM

The interaction of pure aluminum (not covered with an oxide film) with water can be described using the reaction equation:

2Al + 6H2O = 2Al(OH)3 + 3H2.

 When interacting with sea water, pure aluminum begins to corrode, because... sensitive to dissolved salts. To use aluminum in seawater, a small amount of magnesium and silicon is added to its composition. The corrosion resistance of aluminum and its alloys when exposed to sea water is significantly reduced if the metal contains copper.

Corrosion of aluminum in acids

As the purity of aluminum increases, its resistance to acids increases.

Corrosion of aluminum in sulfuric acid

Sulfuric acid (has oxidizing properties) in medium concentrations is very dangerous for aluminum and its alloys. The reaction with dilute sulfuric acid is described by the equation:

 2Al + 3H2SO4(dil) → Al2(SO4)3 + 3H2.

Concentrated cold sulfuric acid has no effect. And when heated, aluminum corrodes:

2Al + 6H2SO4(conc) → Al2(SO4)3 + 3SO2 + 6H2O.

In this case, a soluble salt is formed - aluminum sulfate.

Al is stable in oleum (fuming sulfuric acid) at temperatures up to 200 °C. Due to this, it is used for the production of chlorosulfonic acid (HSO3Cl) and oleum.

Corrosion of aluminum in hydrochloric acid

Aluminum or its alloys quickly dissolve in hydrochloric acid (especially when the temperature rises). Corrosion equation:

2Al + 6HCl → 2AlCl3 + 3H2.

Solutions of hydrobromic (HBr) and hydrofluoric (HF) acids act similarly.

Corrosion of aluminum in nitric acid

A concentrated solution of nitric acid has high oxidizing properties. Aluminum in nitric acid at normal temperatures is extremely resistant (resistance is higher than that of stainless steel 12Х18Н9). It is even used to produce concentrated nitric acid by direct synthesis.

When heated, corrosion of aluminum in nitric acid proceeds according to the reaction:

Al + 6HNO3(conc) → Al(NO3)3 + 3NO2 + 3H2O.

Corrosion of aluminum in acetic acid

Aluminum is quite resistant to acetic acid of any concentration, but only if the temperature does not exceed 65 °C. It is used to produce formaldehyde and acetic acid. At higher temperatures, aluminum dissolves (with the exception of acid concentrations of 98 - 99.8%).

Aluminum is stable in bromic and weak solutions of chromic (up to 10%), phosphoric (up to 1%) acids at room temperature.

Citric, butyric, malic, tartaric, propionic acids, wine, and fruit juices have a weak effect on aluminum and its alloys.

Oxalic, formic, and organochlorine acids destroy metal.

The corrosion resistance of aluminum is greatly influenced by vapor and liquid mercury. After a short contact, the metal and its alloys intensively corrode, forming amalgams.

Corrosion of aluminum in alkalis

Alkalis easily dissolve the protective oxide film on the surface of aluminum, it begins to react with water, as a result of which the metal dissolves with the release of hydrogen (aluminum corrosion with hydrogen depolarization).

2Al + 2NaOH + 6H2O → 2Na[Al(OH)4] + 3H2;

2(NaOH•H2O) + 2Al → 2NaAlO2 + 3H2.

Aluminates are formed.

Also, the oxide film is destroyed by mercury, copper and chlorine ions.

Source: https://www.okorrozii.com/korrozia-aliuminiya.html

Sulfuric acid - chemical properties and industrial production

Physical properties of sulfuric acid:
Heavy oily liquid (“oil of vitriol”);
density 1.84 g/cm3; non-volatile, highly soluble in water - with strong heating; t°pl. = 10.3°C, t°boil. = 296°C, very hygroscopic, has water-removing properties (charring of paper, wood, sugar).

The heat of hydration is so great that the mixture can boil, splash and cause burns. Therefore, it is necessary to add acid to water, and not vice versa, since when water is added to acid, lighter water will end up on the surface of the acid, where all the heat generated will be concentrated.

Industrial production of sulfuric acid (contact method):

1) 4FeS2 + 11O2 → 2Fe2O3 + 8SO2

2) 2SO2 + O2 V2O5→ 2SO3

3) nSO3 + H2SO4 → H2SO4 nSO3 (oleum)

Crushed, purified, wet pyrite (sulfur pyrite) is poured on top into a furnace for firing in a “ fluidized bed .”
Air enriched with oxygen is passed from below (counterflow principle). Furnace gas comes out of the furnace, the composition of which is: SO2, O2, water vapor (the pyrite was wet) and tiny particles of cinder (iron oxide).

The gas is purified from impurities of solid particles (in a cyclone and electric precipitator) and water vapor (in a drying tower).
In a contact apparatus, sulfur dioxide is oxidized using a V2O5 catalyst (vanadium pentoxide) to increase the reaction rate. The process of oxidation of one oxide to another is reversible. Therefore, the optimal conditions for the direct reaction to occur are selected - increased pressure (i.e.

the direct reaction occurs with a decrease in the total volume) and the temperature is not higher than 500 C (since the reaction is exothermic).

In the absorption tower, sulfur oxide (VI) is absorbed by concentrated sulfuric acid.
Absorption by water is not used, because sulfur oxide dissolves in water with the release of a large amount of heat, so the resulting sulfuric acid boils and turns into steam. To prevent the formation of sulfuric acid fog, use 98% concentrated sulfuric acid. Sulfur oxide dissolves very well in such an acid, forming oleum: H2SO4 nSO3

Chemical properties of sulfuric acid:

H2SO4 is a strong dibasic acid, one of the strongest mineral acids; due to its high polarity, the H–O bond is easily broken.

1)   In an aqueous solution, sulfuric acid dissociates , forming a hydrogen ion and an acidic residue:
H2SO4 = H+ + HSO4—;
HSO4— = H+ + SO42-. Summary equation:

H2SO4 = 2H+ + SO42-.

2) Interaction of sulfuric acid with metals : Dilute sulfuric acid dissolves only metals that are in the voltage series to the left of hydrogen:

Zn0 + H2+1SO4(dil) → Zn+2SO4 + H2

3)    Interaction of sulfuric acid with basic oxides:
CuO + H2SO4 → CuSO4 + H2O

4) Interaction of sulfuric acid with hydroxides:
H2SO4 + 2NaOH → Na2SO4 + 2H2O
H2SO4 + Cu(OH)2 → CuSO4 + 2H2O

5) Exchange reactions with salts:
BaCl2 + H2SO4 → BaSO4↓ + 2HCl
The formation of a white precipitate of BaSO4 (insoluble in acids) is used to detect sulfuric acid and soluble sulfates (qualitative reaction to sulfate ion).

Special properties of concentrated H2SO4:

1) Concentrated sulfuric acid is a strong oxidizing agent ; when interacting with metals (except Au, Pt), it is reduced to S+4O2, S0 or H2S-2 depending on the activity of the metal.

Without heating, it does not react with Fe, Al, Cr - passivation.

When interacting with metals of variable valence, the latter are oxidized to higher oxidation states than in the case of a dilute acid solution: Fe0 → Fe3+, Cr0 → Cr3+, Mn0 → Mn4+ , Sn0 → Sn4+

Active metal

8 Al + 15 H2SO4(conc.)→4Al2(SO4)3 + 12H2O + 3 H2S
4│2Al0 – 6 e — → 2Al3+ — oxidation
3│ S6+ + 8e → S2– reduction

4Mg+ 5H2SO4 → 4MgSO4 + H2S + 4H2O

Medium activity metal

2Cr + 4 H2SO4(conc.)→ Cr2(SO4)3 + 4 H2O + S
1│ 2Cr0 – 6e →2Cr3+— oxidation
1│ S6+ + 6e → S0—reduction

Low-active metal

2Bi + 6H2SO4(conc.)→ Bi2(SO4)3 + 6H2O + 3 SO2
1│ 2Bi0 – 6e → 2Bi3+ – oxidation
3│ S6+ + 2e →S4+ – reduction

2Ag + 2H2SO4 →Ag2SO4 + SO2 + 2H2O

2) Concentrated sulfuric acid oxidizes some non-metals, usually to the maximum oxidation state, and is itself reduced to S+4 O2:

C + 2H2SO4(conc) → CO2 + 2SO2 + 2H2O

Source: http://himege.ru/sernaya-kislota-ximicheskie-svojstva-i-promyshlennoe-proizvodstvo/

Lesson 9. Ions in aqueous solution – HIMI4KA

Lessons archive › Basic laws of chemistry

In lesson 9 “ Ions in an aqueous solution ” from the course “ Chemistry for Dummies ” we will consider the dissolution of salt in water, as well as the electrolysis of solutions and molten salts; Let's get acquainted with Faraday's laws for electrolysis and learn how to find electrolysis products. The knowledge base for this lesson will be the material from lesson 8 “structure of salts”.

Dissolving salt in water

We know from the last lesson that salts are difficult to melt and even more difficult to bring to a boil, however, polar liquids such as water are able to dissolve salts without much effort because the partial positive and negative charges on the atoms of polar water molecules are somewhat replace positive and negative ions in the salt crystal lattice. In other words, the water molecules help break down the salt crystal.

The figure shows what happens to positive and negative ions when a crystal of sodium chloride NaCl is dissolved in water. Each Na+ ion is surrounded by water molecules, which face it with negatively charged oxygen atoms. The same thing happens with Cl— ions, which are surrounded by water molecules facing it with their positively charged hydrogen atoms.

The ions from the salt crystal turn out to be hydrated , and the process of adding water molecules to the ions is called hydration . If, as a result of the hydration process, the stability of the ions passing into the solution becomes greater than their stability in the crystal lattice, then the salt dissolves in water. Sodium chloride is an excellent example of a soluble salt.

Conversely, if the hydration energy is too low, then the crystal is a more stable form and does not dissolve in water. Examples of such insoluble salts are barium sulfate (BaSO4) and silver chloride (AgCl). When a crystal dissolves, it does not simply disintegrate into ions, but is separated into ions by the molecules of the liquid in which the dissolution occurs.

 Non-polar liquids (for example, C8H18 gasoline) are NOT capable of separating ions in the crystal lattice of salts.

Electrolysis of solutions and molten salts

Metals conduct current well - every schoolchild knows this. Electrical conductivity in metals is caused by the movement of electrons within them, but the metal ions remain stationary.

Although salt crystals do not conduct current, solutions and molten salts can and practice this, since anions (negative ions) and cations (positive ions) can move in opposite directions if voltage is applied.

The mobility of salt ions is even greater if it has undergone a hydration process.

A long time ago, the English scientist Michael Faraday melted salt (heating it above 801ºC), then immersed two electrodes ( cathode and anode ) in the melt, and then took and passed an electric current through the molten salt. After these manipulations, he noticed that chemical reactions began to take place on the electrodes: sodium ions began to migrate to the cathode (where electrons enter the melt) and are reduced there to metallic sodium

Chloride ions migrate in the other direction - towards the anode, give it their excess electrons and are oxidized to chlorine gas

All this can be depicted using the complete reaction, which is the separation of NaCl into its constituent elements:

The whole process is called electrolysis , which means “tearing apart by electricity.” For electrolysis, it is not necessary to melt the salt; you can also use a regular aqueous solution of salt, because the mobility of ions is even greater if the salt has undergone a hydration process. But then the complete reaction will look different, and not metallic sodium, but hydrogen gas will be released at the cathode:

• Na+ + Cl— + H2O → Na+ + ½Cl2 + ½H2 + OH—

I hope that you are wondering why the product of electrolysis of an aqueous solution is not Na (as it was in molten salt), but ½H2. The explanation is simple: some H2O molecules dissociate into H+ and OH– ions.

Since the H+ ion has a greater affinity for the electron (that is, it attracts it more strongly) than the Na+ ion, the H+ ions are the first to reach the cathode, where they immediately restore the missing electron and turn from the ion into a full-fledged H2 gas, while the Na+ ions remain in solution.

Here is a bun with the products of electrolysis of an aqueous solution of salts, it may be useful - maybe not, but it’s better to take notes:

Meanwhile, Faraday did not sit idle, but observed, conducted experiments, used other electrolytes, increased and decreased the charge and observed again. He eventually noticed a relationship between the amount of electricity supplied and the amount of substances produced. The patterns he established are called Faraday's laws for electrolysis . Let's formulate them:

1. Passing the same electric charge through an electrolytic cell always results in a quantitatively identical chemical transformation in a given reaction. The mass of the element deposited on the electrode is proportional to the amount of charge passed through the electrolytic cell.
2. To release 1 mole of a substance on the electrode, which gains or loses 1 electron during an electrochemical reaction, it is necessary to pass 96,485 coulombs (C) of electricity through the cell. If N electrons are involved in the reaction, N·96485 C of electricity is required to release a mole of product.

An amount of electricity equal to 96485 C is called 1 faraday and is denoted by the symbol F. Faraday's laws become obvious when we consider that 1 F is simply the charge on 1 mole of electrons, i.e. 6.022 1023 electrons. The factor of 6.022-1023, which allows you to go from individual molecules to moles of a substance, also allows you to go from 1 electronic charge to 1 F electric charge.

 Of course, at one time Faraday knew nothing about Avogadro's number or the charge of the electron. However, from the experiments he carried out, he was able to conclude that the charges on the ions are multiples of some elementary unit of charge, so that 96485 C of electricity correspond to 1 mole of such units. The term electron first appeared in 1881; it was introduced by the English physicist J. Stoney to designate the elementary unit of ionic charge.

The term “electron” began to be applied to a real negatively charged particle another 10 years later.

1 example. Write down the equations for the reactions that occur when an electric current is passed through molten NaCl salt. How many grams of sodium and chlorine will be released when 1 F of electricity is passed through an electrolytic cell?

Solution: The equation for the reaction occurring at the cathode is: Na+ + e— → Na, and equation 1 for the anodic reaction is: Cl— → Cl2 + e—. When 1 mole of electrons (1 F) passes through molten salt NaCl, each electron reduces 1 sodium ion, resulting in the formation of 1 mole of sodium atoms.

Consequently, 22.990 g of Na is released at the cathode. At the anode, 1 mole of electrons is removed from 1 mole of chloride ions, after which 1 mole of chlorine atoms remains, which combine in pairs to form 1/2 mole of Cl2 molecules.

Therefore, the mass of chlorine gas released at the anode should be equal to 35.453 g (which is equal to the atomic mass of Cl, or half the molecular weight of Cl).

Example 2: How many grams of magnesium metal and chlorine gas are released when 1 F of electricity is passed through an electrolytic cell containing molten magnesium chloride, MgCl2?
Solution: The reaction Mg2+ + 2e— → Mg occurs at the cathode, and the reaction 2Cl— → Cl2 + 2e— occurs at the anode.

Since each Mg2+ ion requires 2 electrons to reduce, 1 mole of electrons is only sufficient to reduce half a mole of magnesium ions, so 12.153 g of magnesium should be released at the cathode. (The atomic mass of magnesium is 24.305 g/mol.) As in example 1, 1 mole of Cl– ions will oxidize at the anode and half a mole will be released, i.e.

35.453 g, Cl2 gas.

Example 3. The main industrial method for producing aluminum metal is the electrolysis of molten salts containing Al3 + ions. Determine the amount of electric charge, in Faradays and coulombs, that must be passed through the melt to produce 1 kg of metal.

Solution: 1 kg of aluminum contains 1000 g / 26.98 g mol-1 = 37.06 mol atoms. Since each aluminum atom requires 3 electrons to be released, 37.06 moles of atoms will require 3·37.06 = 111.2 moles of electrons.

This amount of electricity is equivalent to 111.2F, or 10,730,000 C.

I hope lesson 9 “ Ions in an aqueous solution ” was informative and understandable. If you have any questions, write them in the comments. If there are no questions, then go to Lesson 10, “Ions in Gas.”

Source: https://himi4ka.ru/arhiv-urokov/urok-9-iony-v-vodnom-rastvore.html

Topic No. 12 “Salts” | CHEM-MIND.com

Determination of salts within the framework of the theory of dissociation. Salts are usually divided into three groups: medium, acidic and basic. In medium salts, all hydrogen atoms of the corresponding acid are replaced by metal atoms, in acidic salts they are only partially replaced, in basic salts of the OH group of the corresponding base they are partially replaced by acidic residues.

There are also some other types of salts, such as double salts, which contain two different cations and one anion: CaCO3 • MgCO3 (dolomite), KCl • NaCl (sylvinite), KAl(SO4)2 (potassium alum); mixed salts containing one cation and two different anions: CaOCl2 (or Ca(OCl)Cl); complex salts, which include a complex ion consisting of a central atom bound to several ligands : K4[Fe(CN)6] (yellow blood salt), K3[Fe(CN)6] (red blood salt), Na[ Al(OH)4], [Ag(NH3)2]Cl; hydrate salts (crystalline hydrates), which contain molecules of water of crystallization: CuSO4 • 5H2O (copper sulfate), Na2SO4 • 10H2O (Glauber’s salt).

The name of the salts is formed from the name of the anion followed by the name of the cation.

For salts of oxygen-free acids, the suffix ide is added to the name of the non-metal , for example sodium chloride NaCl, iron sulfide (H) FeS, etc.

-am is added to the Latin root of the name of the element in the case of higher oxidation states , and the ending -it in the case of lower oxidation states .

In the names of some acids, the prefix hypo- is used to denote the lower oxidation states of a non-metal ; for salts of perchloric and manganese acids, the prefix per- is used, for example: calcium carbonate CaCO3, iron(III) sulfate Fe2(SO4)3, iron(II) sulfite FeSO3, potassium hypochlorite KOSl, potassium chlorite KOSl2, potassium chlorate KOSl3, potassium perchlorate KOSl4, potassium permanganate KMnO4, potassium dichromate K2Cr2O7.

Acidic and basic salts can be considered as the product of incomplete conversion of acids and bases. According to the international nomenclature, the hydrogen atom included in the composition of the acid salt is denoted by the prefix hydro-, the OH group by the prefix hydroxy, NaHS - sodium hydrosulfide, NaHSO3 - sodium hydrosulfite, Mg(OH)Cl - magnesium hydroxychloride, Al(OH)2Cl - aluminum dihydroxychloride .

In the names of complex ions, the ligands are first indicated, followed by the name of the metal, indicating the corresponding oxidation state (in Roman numerals in parentheses).

In the names of complex cations, Russian names of metals are used, for example: [Cu(NH3)4]Cl2 - tetraammine copper(II) chloride, [Ag(NH3)2]2SO4 - diammine silver(1) sulfate.

The names of complex anions use the Latin names of metals with the suffix -at, for example: K[Al(OH)4] - potassium tetrahydroxyaluminate, Na[Cr(OH)4] - sodium tetrahydroxychromate, K4[Fe(CN)6] - potassium hexacyanoferrate(H).

The names of hydrate salts ( crystal hydrates ) are formed in two ways. You can use the naming system for complex cations described above; for example, copper sulfate [Cu(H2O)4]SO4 • H20 (or CuSO4 • 5H2O) can be called tetraaquacopper(II) sulfate.

However, for the most well-known hydrate salts, most often the number of water molecules (degree of hydration) is indicated by a numerical prefix to the word “hydrate”, for example: CuSO4 • 5H2O - copper(I) sulfate pentahydrate, Na2SO4 • 10H2O - sodium sulfate decahydrate, CaCl2 • 2H2O - dihydrate calcium chloride.

Nomenclature of salts

Salt solubility

Based on their solubility in water, salts are divided into soluble (P), insoluble (H) and slightly soluble (M). To determine the solubility of salts, use the table of solubility of acids, bases and salts in water. If you don’t have a table at hand, you can use the rules. They are easy to remember.

1. All salts of nitric acid - nitrates - are soluble.

2. All salts of hydrochloric acid are soluble - chlorides, except AgCl (H), PbCl 2 (M) .

3. All sulfuric acid salts are soluble - sulfates, except BaSO 4 (H)

Source: https://www.chem-mind.com/2017/03/20/%D1%82%D0%B5%D0%BC%D0%B0-%E2%84%9611-%D1%81%D0 %BE%D0%BB%D0%B8/

Dissolution in water: what, how and under what conditions

Water is a universal solvent, adapted to any type of life activity. It dissolves almost any substance, in particular ionic and polar compounds. The unique impact properties are characterized by high dielectric constant. In nature, water contains a lot of substances and compounds that got into it one way or another.

Dissolution process

At first glance, the process of decay is simple, but its essence is much more complex than it looks. That is why there are substances that are soluble in water and insoluble in other liquids. The creation of a solution is associated with physical processes: diffusion describes the very liquefaction of particles as a result of stirring. Hydration is the process by which chemical bonds are formed between water and an added substance.

The dissolution of substances is characterized by:

• the hydration that has occurred;
• change in the color of the solution;
• thermal effects (under certain conditions) and other factors.

Proof of mixing that has occurred is a change in the color of the solution. For example, an admixture of copper sulfate (which is initially white) colors the water an intense blue color. If the chemical properties of the bases are responsible for the color, then the release of heat occurs due to physical reasons. Thus, it is a completely physical-chemical process.

What is a solution

A solution is a homogeneous mixture of substances with a solvent. Soluble substances disintegrate under the action of polar water molecules into small particles, resulting in mixing until completely homogeneous. Aqueous solutions can be colorless or colored, but one thing remains the same - they are transparent regardless of color.

It doesn't matter whether you add water to a substance or sprinkle it. Also, the process will gradually occur without intervention (stirring), in some cases a visible precipitate will form. In other cases, the solution is colored in the color of the added substance, but always remains transparent to light.

Undissolved substances settle to the bottom in a dense layer under the pressure of water. Or they can remain on the surface in the form of uneven particles. Liquids form layers because they have different densities with water. For example, vegetable oil forms a film on the surface.

Which substances dissolve in water and which do not?

Water is truly universal and unique in its properties. Sometimes you need to stir harder to achieve complete destruction of the particles, but for the most part, water blurs any compounds. However, there are substances that even it cannot handle.

There is a condition according to which the amount of water must be greater so that the substances disperse and do not settle to the bottom. Using table salt as an example: when you add a large amount, it stops dissolving and forms a dense, stone-like layer.

In addition, some substances can be removed from the liquid, while others cannot. For example, mercury dissolves in water and the purification process is impossible. Other similar substances found in everyday life: table and sea salt, sugar of any type, baking soda, starch. They are invisible and prone to discoloration of water, but the particles are so small that they simply undergo filtration along with the solution. Bulk substances such as sand or clay do not dissolve, so the water can be filtered.

Classification of abilities by substance:

1. Highly soluble (alcohol, sugar, salt (aka sodium), most alkalis and metal nitrates).
2. Slightly soluble (gypsum, berthollet salt, benzene, methane, nitrogen and oxygen).
3. Practically insoluble (precious and semi-precious metals, kerosene, a number of oils, inert gases, copper sulfide).

A separate group is fat-soluble and water-soluble vitamins. They are necessary for human health, and due to their ability to dissolve, they accumulate in the body due to their water content. The water-soluble type includes vitamins C, B1, B2, B3 (PP), B6, B12, folic acid, pantothenic acid and biotin.

Thus, water as a solvent is quite unique. The list of insoluble substances is complex and short enough to speak of the versatility of water as a solvent.

Source: https://VodaVoMne.ru/svojstva-vody/rastvorenie-v-vode

Solubility of copper in water and acids

The chemical properties of most elements are based on their ability to dissolve in aqueous media and acids. The study of the characteristics of copper is associated with a low-active effect under normal conditions.

A feature of its chemical processes is the formation of compounds with ammonia, mercury, nitric and sulfuric acids. The low solubility of copper in water is not capable of causing corrosion processes.

It has special chemical properties that allow the compound to be used in various industries.

Item Description

Copper is considered the oldest metal, which people learned to mine even before our era. This substance is obtained from natural sources in the form of ore. Copper is an element of the chemical table with the Latin name cuprum, the serial number of which is 29. In the periodic table it is located in the fourth period and belongs to the first group.

The naturally occurring substance is a pink-red heavy metal with a soft and malleable structure. Its boiling and melting point is more than 1000 °C. Considered a good guide.

Chemical structure and properties

If you study the electronic formula of a copper atom, you will find that it has 4 levels. There is only one electron in the 4s valence orbital. During chemical reactions, from 1 to 3 negatively charged particles can be split off from an atom, then copper compounds with an oxidation state of +3, +2, +1 are obtained. Its divalent derivatives are most stable.

In chemical reactions it acts as a low-reactive metal. Under normal conditions, copper has no solubility in water. Corrosion is not observed in dry air, but when heated, the metal surface becomes covered with a black coating of divalent oxide.

The chemical stability of copper is manifested under the action of anhydrous gases, carbon, a number of organic compounds, phenolic resins and alcohols. It is characterized by complex formation reactions with the release of colored compounds.

Copper has slight similarities with alkali group metals due to the formation of monovalent derivatives.

What is solubility?

This is the process of formation of homogeneous systems in the form of solutions when one compound interacts with other substances. Their components are individual molecules, atoms, ions and other particles. The degree of solubility is determined by the concentration of the substance that was dissolved when obtaining a saturated solution.

The unit of measurement is most often percentages, volume fractions or weight fractions. The solubility of copper in water, like other solid compounds, is subject only to changes in temperature conditions. This dependence is expressed using curves. If the indicator is very small, then the substance is considered insoluble.

The metal exhibits corrosion resistance when exposed to sea water. This proves its inertness under normal conditions. The solubility of copper in water (fresh) is practically not observed. But in a humid environment and under the influence of carbon dioxide, a green film forms on the metal surface, which is the main carbonate:

Cu + Cu + O2 + H2O + CO2 → Cu(OH)2 · CuCO2.

If we consider its monovalent compounds in the form of salts, then their insignificant dissolution is observed. Such substances are subject to rapid oxidation. The result is divalent copper compounds. These salts have good solubility in aqueous media. Their complete dissociation into ions occurs.

Solubility in acids

The usual conditions for reactions of copper with weak or dilute acids do not favor their interaction. The chemical process of the metal with alkalis is not observed. Copper solubility in acids is possible if they are strong oxidizing agents. Only in this case does interaction take place.

Solubility of copper in nitric acid

This reaction is possible due to the fact that the process of oxidation of the metal with a strong reagent occurs. Nitric acid in diluted and concentrated form exhibits oxidizing properties with the dissolution of copper.

In the first option, the reaction produces copper nitrate and nitrogen divalent oxide in a ratio of 75% to 25%. The process with dilute nitric acid can be described by the following equation:

8HNO3 + 3Cu → 3Cu(NO3)2 + NO + NO + 4H2O.

In the second case, copper nitrate and nitrogen oxides are obtained, divalent and tetravalent, the ratio of which is 1 to 1. This process involves 1 mole of metal and 3 moles of concentrated nitric acid. When copper dissolves, the solution heats up strongly, resulting in thermal decomposition of the oxidizing agent and the release of an additional volume of nitrogen oxides:

4HNO3 + Cu → Cu(NO3)2 + NO2 + NO2 + 2H2O.

The reaction is used in small-scale production associated with recycling scrap or removing coatings from waste. However, this method of dissolving copper has a number of disadvantages associated with the release of large amounts of nitrogen oxides. To capture or neutralize them, special equipment is required. These processes are very expensive.

The dissolution of copper is considered complete when the production of volatile nitrogen oxides completely ceases. The reaction temperature ranges from 60 to 70 °C. The next step is to drain the solution from the chemical reactor. At its bottom there are small pieces of metal that have not reacted. Water is added to the resulting liquid and filtered.

Solubility in sulfuric acid

Under normal conditions, this reaction does not occur. The factor determining the dissolution of copper in sulfuric acid is its strong concentration. A dilute medium cannot oxidize the metal. The dissolution of copper in concentrated sulfuric acid proceeds with the release of sulfate.

The process is expressed by the following equation:

Cu + H2SO4 + H2SO4 → CuSO4 + 2H2O + SO2.

Properties of copper sulfate

Dibasic salt is also called sulfuric acid and is designated as CuSO4. It is a substance without a characteristic odor and does not exhibit volatility. In its anhydrous form, salt is colorless, opaque, and highly hygroscopic. Copper (sulfate) has good solubility. Water molecules, when added to salt, can form crystalline hydrate compounds. An example is copper sulfate, which is a blue pentahydrate. Its formula: CuSO4·5H2O.

Crystalline hydrates have a transparent structure with a bluish tint and exhibit a bitter, metallic taste. Their molecules are capable of losing bound water over time. They are found in nature in the form of minerals, which include chalcanthite and butite.

Susceptible to copper sulfate. Solubility is an exothermic reaction. The process of salt hydration generates a significant amount of heat.

Solubility of copper in iron

As a result of this process, pseudo-alloys of Fe and Cu are formed. For metallic iron and copper, limited mutual solubility is possible. Its maximum values ​​are observed at a temperature of 1099.85 °C. The degree of solubility of copper in the solid form of iron is 8.5%. These are small numbers. The dissolution of metallic iron in the solid form of copper is about 4.2%.

Reducing the temperature to room values ​​makes the mutual processes insignificant. When metallic copper is melted, it is able to well wet iron in solid form. When producing Fe and Cu pseudo-alloys, special blanks are used. They are created by pressing or baking iron powder in pure or alloyed form. Such workpieces are impregnated with liquid copper, forming pseudo-alloys.

Dissolution in ammonia

The process often occurs by passing NH3 in gaseous form over hot metal. The result is the dissolution of copper in ammonia, the release of Cu3N. This compound is called monovalent nitride.

Its salts are exposed to ammonia solution. The addition of such a reagent to copper chloride leads to the formation of a precipitate in the form of hydroxide:

CuCl2 + NH3 + NH3 + 2H2O → 2NH4Cl + Cu(OH)2↓.

Excess ammonia promotes the formation of a complex type compound that is dark blue in color:

Cu(OH)2↓+ 4NH3 → [Cu(NH3)4] (OH)2.

This process is used to determine cupric ions.

Solubility in cast iron

In the structure of malleable pearlitic cast iron, in addition to the main components, there is an additional element in the form of ordinary copper. It is this that increases the graphitization of carbon atoms and helps to increase the fluidity, strength and hardness of alloys.

The metal has a positive effect on the level of perlite in the final product. The solubility of copper in cast iron is used to alloy the original composition. The main purpose of this process is to obtain a malleable alloy.

It will have increased mechanical and corrosion properties, but reduced embrittlement.

If the copper content in cast iron is about 1%, then the tensile strength is equal to 40%, and the yield strength increases to 50%. This significantly changes the characteristics of the alloy.

Increasing the amount of metal alloying to 2% leads to a change in strength to 65%, and the fluidity rate becomes 70%. With a higher copper content in cast iron, spheroidal graphite is more difficult to form. The introduction of an alloying element into the structure does not change the technology for forming a viscous and soft alloy.

The time allotted for annealing coincides with the duration of such a reaction in the production of cast iron without copper admixture. It is about 10 hours.

The use of copper for the production of cast iron with a high silicon concentration is not able to completely eliminate the so-called ferruginization of the mixture during annealing. The result is a product with low elasticity.

Solubility in mercury

When mercury is mixed with metals of other elements, amalgams are obtained. This process can take place at room temperature, because under such conditions Pb is a liquid. The solubility of copper in mercury disappears only during heating. The metal must first be crushed.

When solid copper is wetted with liquid mercury, mutual penetration of one substance into another or a process of diffusion occurs. The solubility value is expressed as a percentage and is 7.4*10-3. The reaction produces a hard, simple amalgam similar to cement. If you heat it up a little, it softens.

As a result, this mixture is used to repair porcelain products. There are also complex amalgams with an optimal content of metals. For example, dental alloy contains the elements silver, tin, copper and zinc. Their percentage ratio is 65: 27: 6:2. Amalgam with this composition is called silver.

Each component of the alloy performs a specific function, which allows you to obtain a high-quality filling.

Another example is an amalgam alloy, which has a high copper content. It is also called copper alloy. The amalgam contains from 10 to 30% Cu. The high copper content prevents the interaction of tin with mercury, which prevents the formation of a very weak and corrosive phase of the alloy. In addition, reducing the amount of silver in a filling leads to cheaper prices.

To prepare amalgam, it is advisable to use an inert atmosphere or a protective liquid that forms a film. The metals that make up the alloy can be quickly oxidized by air. The process of heating cuprum amalgam in the presence of hydrogen causes the mercury to be distilled off, allowing the elemental copper to be separated. As you can see, this topic is not difficult to learn.

Now you know how copper interacts not only with water, but also with acids and other elements.

Source: https://FB.ru/article/238897/rastvorimost-medi-v-vode-i-kislotah

Hydrochloric acid is one of the strongest acids, an extremely popular reagent

• Hydrochloric acid is an inorganic substance, a monobasic acid, one of the strongest acids. Other names are also used: hydrogen chloride, hydrochloric acid, hydrochloric acid. Acid in its pure form is a colorless and odorless liquid. Industrial acid usually contains impurities that give it a slightly yellowish tint. Hydrochloric acid is often called “fuming” because it emits hydrogen chloride vapors, which react with moisture in the air and form acid fog. Very soluble in water. At room temperature, the maximum possible hydrogen chloride content by weight is 38%. An acid with a concentration greater than 24% is considered concentrated. Hydrochloric acid actively reacts with metals, oxides, and hydroxides, forming salts - chlorides. HCl reacts with salts of weaker acids; with strong oxidizing agents and ammonia. To determine hydrochloric acid or chlorides, use a reaction with silver nitrate AgNO3, which results in the formation of a white cheesy precipitate.
  

  Safety precautions

  The substance is very caustic, corrodes skin, organic materials, metals and their oxides. When exposed to air, it releases hydrogen chloride vapors, which cause suffocation, burns to the skin, mucous membranes of the eyes and nose, damage the respiratory system, and destroy teeth. Hydrochloric acid belongs to substances of the 2nd degree of danger (highly dangerous), the maximum permissible concentration of the reagent in the air is 0.005 mg/l. You can work with hydrogen chloride only in filter gas masks and protective clothing, including rubber gloves, an apron, and safety shoes. When acid spills, it is washed off with plenty of water or neutralized with alkaline solutions. Those affected by the acid should be taken out of the danger zone, rinse their skin and eyes with water or soda solution, and call a doctor. The chemical reagent can be transported and stored in glass, plastic containers, as well as in metal containers coated on the inside with a rubber layer. The container must be hermetically sealed.

  Receipt

  On an industrial scale, hydrochloric acid is produced from hydrogen chloride (HCl) gas. Hydrogen chloride itself is produced in two main ways: - by the exothermic reaction of chlorine and hydrogen - thus obtaining a high-purity reagent, for example, for the food industry and pharmaceuticals; - from accompanying industrial gases - an acid based on such HCl is called free gas.

This is interesting

It was hydrochloric acid that nature “entrusted” with the process of breaking down food in the body. The concentration of acid in the stomach is only 0.4%, but this is enough to digest a razor blade in a week!

Acid is produced by the cells of the stomach itself, which is protected from this aggressive substance by the mucous membrane. However, its surface is renewed daily to restore damaged areas. In addition to participating in the process of digesting food, acid also performs a protective function, killing pathogens that enter the body through the stomach.

What substances does gold react with, what properties does it have?

What reacts to gold and what substances will help to recognize the metal under normal conditions or in the laboratory? This is a difficult question, since at its core it is an element of the periodic table, which is characterized by inertia.

articles

• Metal properties
• Physical indicators
• Areas of application

Dissolving gold in aqua regia

Inertness is the ability of a substance not to react to acids, alkalis and not to oxidize upon contact with air and water. In the table, the metal is designated by the symbol Au, and “gold” is translated from Latin as “sunrise”.

Gold and platinum just began to be called noble metals when their ability not to react to external factors and chemical reagents was discovered.

But chemistry, like any other science, does not stand still, and several substances have been discovered that react with Au.

Metal properties

The chemical properties of gold indicate that this metal can still react to certain substances.

So what does Au interact with and under what conditions?

• Mercury can form a special compound with gold - an amalgam. It is an alloy of two metals; mercury molecules attract Au molecules, resulting in a compound.
• Gold dissolves in aqua regia, this has been known for quite some time, but the mixture of high concentrations of nitric and hydrochloric acids has no analogues. Chemists still use it to this day; they have not found a worthy replacement for aqua regia and use it when carrying out refining.
• The reaction of selenic acid and Au begins only when the concentrated acid is heated to a certain temperature.
• Another noble metal reacts with potassium iodide. But in some cases, for identification they use a regular solution of iodine in alcohol, which is present in the first aid kit.
• Liquid bromine and water with cyanide are two other chemicals that can react with Au.

The ability of mercury to attract Au molecules has been known for a long time. In ancient times, this property of the metal was used to mine gold. Special gateways were created, the surface of which was covered with a layer of mercury, which attracted Au and made it possible to increase the level of its production. The disadvantage of this method was toxicity; a person who had constant contact with mercury sacrificed his health by mining gold.

Amalgam is a reversible condition; in order for Au to regain its original appearance, the mixture must be heated to approximately 800 degrees.

Long before Dmitri Mendeleev dreamed of his periodic table, alchemists knew the ability of gold to dissolve in a mixture of two acids. Nitric and hydrochloric acids were mixed and used to carry out various experiments. Scientists of that time encrypted their notes; for this reason, they did not describe the reaction, but drew it.

Alchemists depicted a lion that absorbed the sun, the animal stood on its hind legs and ate a yellow circle. Gold was associated with the sun for its color, but the lion was just a mixture of two acids. Aqua regia, in fact, is a universal solvent that can decompose all noble metals into molecules. The mixture of acids is still used today when carrying out refining or other experiments. Aqua regia formula: HNO3+3 HCl.

Reaction of gold to iodine

This mixture can even dissolve platinum and most existing metals. Only silver does not dissolve too readily in a mixture of two acids. But over time, the strength of the solvent decreases: the more the reagent comes into contact with air, the weaker it becomes.

The reaction with selenic acid takes place under certain conditions. To dissolve gold, it is necessary to use concentrated acid, heat it to a certain temperature and at the same time provide an influx of oxygen. If there is not enough oxygen, the reaction will proceed slowly.

Potassium iodide is used quite rarely in chemistry; they do not like to identify Au in this way. But in everyday life, jewelry made from gold is often checked for authenticity using a solution of iodine in alcohol.

If we talk about industrial applications, the ability of cyanide to interact with the yellow metal has found its place in this industry. Cyanidation is one of the gold purification methods, it helps to separate Au from rock particles and impurities.

Despite its inertness, there is one fact worth considering when working with Au. If the metal and other reagents are heated, the reaction will proceed faster. But gold very quickly returns to its original state, which must be kept in mind.

The list of substances that can react with a noble metal is exhausted. Gold does not dissolve in water, alcohol and other substances. Reagents are not capable of harming the metal or breaking it down into molecules, but do not forget that pure gold is found only in ingots. Even in nature, this metal has impurities that significantly reduce its inertness.

Having assessed all the properties of Au, scientists came to the conclusion that the element on our planet appeared from space. Gold came to Earth with particles of cosmic bodies and meteorites. There were no conditions on our planet favorable for its formation.

The chemical properties of element number 79 are few, but they still help chemists conduct experiments and research, and make new discoveries. But not only chemistry helps to identify a noble metal; there is also another science that has succeeded quite well in this.

Physical indicators

Along with chemical properties, gold also has physical properties, which include:

1. Low hardness, on the Mohs scale from 2.5 to 3 units.
2. Plasticity and malleability.
3. Yellow.

Au does not have high hardness. While diamond is rated 9 on the Mohs scale, this element is rated only 3. To increase the hardness of Au, it is alloyed with other metals to create an alloy used to create jewelry. Jewelry made of pure gold is practically never found; they are heavy and easily deformed when worn.

In order to identify the metal, it is enough to try it on the tooth. You can bite the product, if it is easily deformed and changes shape, if there are teeth marks on the surface, then there is no doubt about its authenticity.

Au is malleable and ductile. You can cut an ingot with a knife without much effort, and you can also turn a piece of precious metal into a thin sheet. Thanks to this, gold leaf is created, which is used as a decorative material: it covers the domes of churches, protecting them from the effects of environmental factors.

Gold is the only metal that has a yellow color. This shade influenced the characteristics of the element and was associated with the power of the sun. Various properties were assigned to the metal; the warm shade also testified to the mysterious origin of the element.

From time immemorial, people have associated Au with wealth and a high position in society. In the old days, ordinary people were not allowed to wear gold jewelry, since only members of high society were worthy of this prerogative.

Areas of application

Due to its properties, beauty and inertness, Au has found application in various industries and beyond.

It is used today:

• in the jewelry industry;
• in cosmetology and medicine;
• for creating electronics;
• in the space industry.

Naturally, the largest part of the precious metal is used to create works of the jewelry industry. Jewelry is made from it, inlaid with precious and semi-precious stones. In addition, gold bars are used as an investment material, money is invested in them, and this invariably brings profit.

A large number of skin care products contain Au. This element helps to cope with the signs of aging, for example, threads of gold that are implanted into the skin and which have a rejuvenating effect on the body. Metal is also used in the treatment of joint diseases (arthritis), and it is also used to treat autoimmune and oncological diseases. A special serum containing Au is injected into the patient’s body.

The contacts of motherboards of computers and mobile phones contain Au in small quantities; they are coated with gold.

If we talk about the space industry, then the element is used wherever its anti-corrosion properties are needed. Gold covers the glass of shuttles and astronaut helmets. And also some parts of contacts in the manufacture of spaceships.

Gold is the most popular metal on the planet; its mining has been going on for so long that it is difficult to determine the date when exactly humanity became acquainted with Au. But we can say for sure that this happened long before our era. Over the years, the popularity of Au only grows, the price of the metal rises, the size of production falls, but mankind’s love for gold does not decrease. It is assigned magical properties, endowed with the energy of the sun and is called either the metal of God or the devil.

The reason for the “special attitude” to gold is not only its beauty, but also the properties that make the metal noble and so valuable to humans.

Source: https://DedPodaril.com/zoloto/imform/chto-reagiruet-na-zoloto.html

What gold dissolves in: a review of chemicals, the use of acids, which method is suitable for home use

Good afternoon, readers! In this article you will find information about one of the most complex processes in chemistry - the dissolution of gold. With the help of my tips, you can recreate the most severe reaction yourself and without special skills!

Gold is a fairly low-active metal. In nature, it is most often found as compounds. When an inexperienced chemist sets out to obtain pure precious metal, the question naturally arises in what gold dissolves. It is impossible to isolate it without dissolution. But finding a substance that will undergo a complex reaction is not an easy task; it’s not for nothing that gold is called a noble metal.

How can you dissolve gold?

For many years, chemists used only a dangerous method in which, at extremely high temperatures, gold dissolves in a reaction with fluorine. But in the modern world, new, safer methods are being used.

Amalgam

Amalgam is an alloy of mercury in a liquid or solid state and is used as an industrial refining method. The process of gold amalgamation involves the ability of mercury to form compounds of several metals.

Before amalgamation, the nugget should be placed in a solution of nitric acid in a ratio of 10:1 with water. The gold must remain in solution until the visible reaction is complete, after which it must be washed.

For amalgamation, precious metal and mercury are taken in equal proportions. Place both substances in a non-metallic tray and rotate it. A ball of mercury dissolves in the molecules of the nugget. Unnecessary sediment is poured out of the tray.

The amalgam saturated with gold must be washed carefully under running water.

Excess mercury from the amalgam is removed by pressing the ball through wet suede. The compound remaining on the surface is heated until the mercury completely evaporates.

Aqua regia

Most acids have a terrible effect on organic matter. But even in them gold does not dissolve. Lomonosov's famous invention - aqua regia - is the only acid capable of starting the reaction.

Aqua regia is a mixture of hydrochloric and nitric acid in a special ratio (1:3). Its properties are greatly enhanced due to the high concentration of components.

The precious metal dissolves in aqua regia due to the fact that nitric acid oxidizes hydrochloric acid. A special compound is formed - atomic chlorine, which instantly reacts with the metal, creating complex chlorauric acid. Part of the precious metal crystallizes, and the other part dissolves.

It is worth noting that the occurrence of a chemical reaction depends on what acid the metal is dissolved in and what its concentration is.

Bleaching

Chlorine, widely used in everyday life, is an aqueous solution of chlorine gas, which belongs to the group of halogens. For refining, bleach purchased in a regular store is not suitable, because... its concentration is too low.

A concentrated solution of chlorine has the following effect: chlorine breaks down into hydrochloric and hypochlorous acids, the second, in turn, under the influence of sunlight, decomposes into hydrochloric acid and oxygen. As in the reaction with aqua regia, an atomic substance is released that easily oxidizes the nugget.

Iodine itself is an insoluble substance in water. Its compound with potassium iodide dissolves. This is a medicine called Lugol.

Gold dissolves in Lugol due to the fact that iodine creates weak compounds - anions. But the reaction is much slower than with acids, and only the top layer of metal dissolves.

Which method is suitable for home use?

Gold refining (obtaining pure metal) can be done at home. The safest method of dissolution is using electric current.

Electrolysis

A large bath is filled with hydrochloric acid and gold chloride, a reagent used to test products and determine the sample. It can be isolated using aqua regia, gold and ammonia or purchased ready-made in jewelry supply stores.

The reaction, called electrochemical, occurs due to the voltage applied to the bath. As a result, high-grade metal without impurities settles on the sides, and the remaining components precipitate at the bottom of the bath.

Step-by-step instructions for dissolving gold

Dissolving metal is a labor-intensive process. An effective way is to use zinc. It is used by chemists to isolate the purest metal of high purity.

There are many videos that clearly show a violent reaction with zinc.

Required materials and tools

The following tools are required:

• heating container;
• large tweezers;
• plate;
• fireproof flask;
• cap with a slot;
• apparatus for melting metals.

Source: https://zhazhdazolota.ru/dobycha/v-chem-rastvoryaetsya-aurum