The chemical properties of most elements are based on their ability to dissolve in water and acids. The study of the characteristics of copper is associated with low activity 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 of the metals that people learned to extract even before our era. This substance is obtained from natural sources in the form of ore. Copper is called an element of the chemical table with the Latin name cuprum, whose serial number is 29. In the periodic system, it is located in the fourth period and belongs to the first group.
The natural substance is a pink-red heavy metal with a soft and malleable texture. Its boiling and melting point isover 1000 °C. Considered a good conductor.
Chemical structure and properties
If you study the electronic formula of the copper atom, you will find that it has 4 levels. There is only one electron in the valence 4s 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 the most stable.
In chemical reactions, it acts as an inactive metal. Under normal conditions, the solubility of copper in water is absent. In dry air, corrosion is not observed, but when heated, the metal surface is 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 a slight similarity to the alkali group metals, associated with the formation of derivatives of the monovalent series.
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 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.
Solubility of copper in water
Metal exhibits corrosion resistance under the action of sea water. This proves its inertia under normal conditions. The solubility of copper in water (fresh water) is practically not observed. But in a humid environment and under the action of carbon dioxide, a green film is formed 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 a s alt, then their slight dissolution is observed. Such substances are subject to rapid oxidation. As a result, divalent copper compounds are obtained. These s alts have good solubility in aqueous media. Their complete dissociation into ions occurs.
Solubility in acids
Normal reactions of copper with weak or dilute acids do not favor their interaction. The chemical process of the metal with alkalis is not observed. The solubility of copper in acids is possible if they are strong oxidizing agents. Only in this case does the interaction take place.
Solubility of copper in nitric acid
Such a reaction is possible due to the fact that the metal is oxidized with a strong reagent. Nitric acid in dilute and concentratedform exhibits oxidizing properties with the dissolution of copper.
In the first variant, during the reaction, copper nitrate and nitrogen divalent oxide are obtained 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 mol of metal and 3 mol of concentrated nitric acid. When copper is dissolved, the solution is strongly heated, resulting in thermal decomposition of the oxidizer and the release of an additional volume of nitric oxides:
4HNO3 + Cu → Cu(NO3)2 + NO 2 + NO2 + 2H2O.
The reaction is used in small-scale production associated with the processing of scrap or the removal of coatings from waste. However, this method of dissolving copper has a number of disadvantages associated with the release of a large amount of nitrogen oxides. To capture or neutralize them, special equipment is required. These processes are very costly.
The dissolution of copper is considered complete when there is a complete cessation of the production of volatile nitrogenous oxides. 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 andfiltering.
Solubility in sulfuric acid
In the normal state, such a 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 + H2SO 4 → CuSO4 + 2H2O + SO2.
Properties of copper sulfate
Dibasic s alt is also called sulfate, denoted as follows: CuSO4. It is a substance without a characteristic odor, not showing volatility. In the anhydrous form, the s alt has no color, it is opaque and highly hygroscopic. Copper (sulfate) has good solubility. Water molecules, joining the s alt, can form crystal hydrate compounds. An example is copper sulfate, which is a blue pentahydrate. Its formula is: CuSO4 5H2O.
Crystal hydrates have a transparent structure of a bluish tint, they exhibit a bitter, metallic taste. Their molecules are capable of losing bound water over time. In nature, they occur in the form of minerals, which include chalcanthite and butite.
Affected by copper sulfate. Solubility is an exothermic reaction. In the process of s alt hydration, a significant amount ofheat.
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 index of 1099.85 °C. The degree of solubility of copper in the solid form of iron is 8.5%. These are small figures. The dissolution of metallic iron in the solid form of copper is about 4.2%.
Reducing the temperature to room values makes mutual processes insignificant. When metallic copper is melted, it is able to wet iron well in solid form. When obtaining Fe and Cu pseudo-alloys, special workpieces are used. They are created by pressing or baking iron powder, which is in pure or alloyed form. Such blanks are impregnated with liquid copper, forming pseudo-alloys.
Dissolving in ammonia
The process often proceeds 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 s alts are exposed to ammonia solution. The addition of such a reagent to copper chloride leads to precipitation in the form of hydroxide:
CuCl2 + NH3 + NH3 + 2H 2O → 2NH4Cl + Cu(OH)2↓.
Ammonia excess contributes to the formation of a complex type compound with a dark blue color:
Cu(OH)2↓+ 4NH3 → [Cu(NH3)4] (OH)2.
This process is used to determine cuprous ions.
Solubility in cast iron
In the structure of ductile pearlitic iron, in addition to the main components, there is an additional element in the form of ordinary copper. It is she who increases the graphitization of carbon atoms, contributes to an increase in 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 carry out alloying of the initial composition. The main purpose of this process is to obtain a malleable alloy. It will have improved 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 fluidity increases to 50%. This significantly changes the characteristics of the alloy. An increase in the amount of alloying metal to 2% leads to a change in strength to a value of 65%, and the yield index becomes 70%. With a higher copper content in the composition of cast iron, nodular graphite is more difficult to form. The introduction of an alloying element into the structure does not change the technology of forming a tough and soft alloy. The time allotted for annealing coincides with the duration of such a reaction in the production of cast iron without copper impurities. It is about 10 hours.
The use of copper to make highsilicon 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 passes 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 diffusion process occurs. The solubility value is expressed as a percentage and is 7.410-3. The reaction produces a solid simple amalgam, similar to cement. If you heat it up a bit, it will soften. As a result, this mixture is used to repair porcelain items. There are also complex amalgams with an optimal metal content. For example, the elements of silver, tin, copper and zinc are present in a dental alloy. Their number in percentage refers as 65:27:6:2. Amalgam with this composition is called silver. Each component of the alloy performs a specific function, which allows you to get a high quality filling.
Another example is the amalgam alloy, which has a high copper content. It is also called copper alloy. The composition of 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. ExceptIn addition, a decrease in the amount of silver in the filling leads to a reduction in price. For the preparation of amalgam, it is desirable to use an inert atmosphere or a protective liquid that forms a film. The metals that make up the alloy are able to quickly oxidize with air. The process of heating cuprum amalgam in the presence of hydrogen leads to the distillation of mercury, which allows the separation of elemental copper. As you can see, this topic is easy to learn. Now you know how copper interacts not only with water, but also with acids and other elements.
