Chemical properties of copper
Copper (Cu) belongs to the d-elements and is located in group IB of D.I. Mendeleev’s periodic table. The electronic configuration of the copper atom in the ground state is written as 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 1 instead of the expected formula 1s 2 2s 2 2p 6 3s 2 3p 6 3d 9 4s 2. In other words, in the case of the copper atom, a so-called “electron jump” from the 4s sublevel to the 3d sublevel is observed. For copper, in addition to zero, oxidation states +1 and +2 are possible. The +1 oxidation state is prone to disproportionation and is stable only in insoluble compounds such as CuI, CuCl, Cu 2 O, etc., as well as in complex compounds, for example, Cl and OH. Copper compounds in the +1 oxidation state do not have a specific color. Thus, copper (I) oxide, depending on the size of the crystals, can be dark red (large crystals) and yellow (small crystals), CuCl and CuI are white, and Cu 2 S is black and blue. The oxidation state of copper equal to +2 is more chemically stable. Salts containing copper in this oxidation state are blue and blue-green in color.
Copper is a very soft, malleable and ductile metal with high electrical and thermal conductivity. The color of metallic copper is red-pink. Copper is located in the activity series of metals to the right of hydrogen, i.e. belongs to low-active metals.
with oxygen
Under normal conditions, copper does not interact with oxygen. Heat is required for the reaction between them to occur. Depending on excess or deficiency of oxygen and temperature conditions, copper (II) oxide and copper (I) oxide can form:
with sulfur
The reaction of sulfur with copper, depending on the conditions, can lead to the formation of both copper (I) sulfide and copper (II) sulfide. When a mixture of powdered Cu and S is heated to a temperature of 300-400 o C, copper (I) sulfide is formed:
If there is a lack of sulfur and the reaction is carried out at temperatures above 400 o C, copper (II) sulfide is formed. However, a simpler way to obtain copper (II) sulfide from simple substances is the interaction of copper with sulfur dissolved in carbon disulfide:
This reaction occurs at room temperature.
with halogens
Copper reacts with fluorine, chlorine and bromine, forming halides with the general formula CuHal 2, where Hal is F, Cl or Br:
Cu + Br 2 = CuBr 2
In the case of iodine, the weakest oxidizing agent among the halogens, copper (I) iodide is formed:
Copper does not interact with hydrogen, nitrogen, carbon and silicon.
with non-oxidizing acids
Almost all acids are non-oxidizing acids, except concentrated sulfuric acid and nitric acid of any concentration. Since non-oxidizing acids are able to oxidize only metals in the activity series up to hydrogen; this means that copper does not react with such acids.
with oxidizing acids
- concentrated sulfuric acid
Copper reacts with concentrated sulfuric acid both when heated and at room temperature. When heated, the reaction proceeds according to the equation:
Since copper is not a strong reducing agent, sulfur is reduced in this reaction only to the +4 oxidation state (in SO 2).
- with dilute nitric acid
The reaction of copper with dilute HNO 3 leads to the formation of copper (II) nitrate and nitrogen monoxide:
3Cu + 8HNO 3 (diluted) = 3Cu(NO 3) 2 + 2NO + 4H 2 O
- with concentrated nitric acid
Concentrated HNO 3 reacts easily with copper under normal conditions. The difference between the reaction of copper with concentrated nitric acid and the reaction with dilute nitric acid lies in the product of nitrogen reduction. In the case of concentrated HNO 3, nitrogen is reduced to a lesser extent: instead of nitric oxide (II), nitric oxide (IV) is formed, which is due to greater competition between nitric acid molecules in concentrated acid for reducing agent (Cu) electrons:
Cu + 4HNO 3 = Cu(NO 3) 2 + 2NO 2 + 2H 2 O
with non-metal oxides
Copper reacts with some non-metal oxides. For example, with oxides such as NO 2, NO, N 2 O, copper is oxidized to copper (II) oxide, and nitrogen is reduced to oxidation state 0, i.e. a simple substance N 2 is formed:
In the case of sulfur dioxide, copper(I) sulfide is formed instead of the simple substance (sulfur). This is due to the fact that copper and sulfur, unlike nitrogen, react:
with metal oxides
When metallic copper is sintered with copper (II) oxide at a temperature of 1000-2000 o C, copper (I) oxide can be obtained:
Also, metallic copper can reduce iron (III) oxide to iron (II) oxide upon calcination:
with metal salts
Copper displaces less active metals (to the right of it in the activity series) from solutions of their salts:
Cu + 2AgNO 3 = Cu(NO 3) 2 + 2Ag↓
An interesting reaction also takes place in which copper dissolves in the salt of a more active metal - iron in the +3 oxidation state. However, there are no contradictions, because copper does not displace iron from its salt, but only reduces it from the oxidation state +3 to the oxidation state +2:
Fe 2 (SO 4) 3 + Cu = CuSO 4 + 2FeSO 4
Cu + 2FeCl 3 = CuCl 2 + 2FeCl 2
The latter reaction is used in the production of microcircuits at the stage of etching copper circuit boards.
Copper corrosion
Copper corrodes over time when in contact with moisture, carbon dioxide and atmospheric oxygen:
2Cu + H 2 O + CO 2 + O 2 = (CuOH) 2 CO 3
As a result of this reaction, copper products are covered with a loose blue-green coating of copper (II) hydroxycarbonate.
Chemical properties of zinc
Zinc Zn is in group IIB of the IV period. The electronic configuration of the valence orbitals of the atoms of a chemical element in the ground state is 3d 10 4s 2. For zinc, only one single oxidation state is possible, equal to +2. Zinc oxide ZnO and zinc hydroxide Zn(OH) 2 have pronounced amphoteric properties.
Zinc tarnishes when stored in air, becoming covered with a thin layer of ZnO oxide. Oxidation occurs especially easily at high humidity and in the presence of carbon dioxide due to the reaction:
2Zn + H 2 O + O 2 + CO 2 → Zn 2 (OH) 2 CO 3
Zinc vapor burns in air, and a thin strip of zinc, after being incandescent in a burner flame, burns with a greenish flame:
When heated, metallic zinc also interacts with halogens, sulfur, and phosphorus:
Zinc does not react directly with hydrogen, nitrogen, carbon, silicon and boron.
Zinc reacts with non-oxidizing acids to release hydrogen:
Zn + H 2 SO 4 (20%) → ZnSO 4 + H 2
Zn + 2HCl → ZnCl 2 + H 2
Technical zinc is especially easily soluble in acids, since it contains impurities of other less active metals, in particular cadmium and copper. High-purity zinc is resistant to acids for certain reasons. To speed up the reaction, a high-purity sample of zinc is brought into contact with copper or a little copper salt is added to the acid solution.
At a temperature of 800-900 o C (red heat), zinc metal, being in a molten state, interacts with superheated water vapor, releasing hydrogen from it:
Zn + H 2 O = ZnO + H 2
Zinc also reacts with oxidizing acids: concentrated sulfuric and nitric.
Zinc as an active metal can form sulfur dioxide, elemental sulfur and even hydrogen sulfide with concentrated sulfuric acid.
Zn + 2H 2 SO 4 = ZnSO 4 + SO 2 + 2H 2 O
The composition of the reduction products of nitric acid is determined by the concentration of the solution:
Zn + 4HNO 3 (conc.) = Zn(NO 3) 2 + 2NO 2 + 2H 2 O
3Zn + 8HNO 3 (40%) = 3Zn(NO 3) 2 + 2NO + 4H 2 O
4Zn +10HNO 3 (20%) = 4Zn(NO 3) 2 + N 2 O + 5H 2 O
5Zn + 12HNO 3 (6%) = 5Zn(NO 3) 2 + N 2 + 6H 2 O
4Zn + 10HNO3 (0.5%) = 4Zn(NO3)2 + NH4NO3 + 3H2O
The direction of the process is also influenced by temperature, amount of acid, purity of the metal, and reaction time.
Zinc reacts with alkali solutions to form tetrahydroxycinates and hydrogen:
Zn + 2NaOH + 2H 2 O = Na 2 + H 2
Zn + Ba(OH) 2 + 2H 2 O = Ba + H 2
When fused with anhydrous alkalis, zinc forms zincates and hydrogen:
In a highly alkaline environment, zinc is an extremely strong reducing agent, capable of reducing nitrogen in nitrates and nitrites to ammonia:
4Zn + NaNO 3 + 7NaOH + 6H 2 O → 4Na 2 + NH 3
Due to complexation, zinc slowly dissolves in ammonia solution, reducing hydrogen:
Zn + 4NH 3 H 2 O → (OH) 2 + H 2 + 2H 2 O
Zinc also reduces less active metals (to the right of it in the activity series) from aqueous solutions of their salts:
Zn + CuCl 2 = Cu + ZnCl 2
Zn + FeSO 4 = Fe + ZnSO 4
Chemical properties of chromium
Chromium is an element of group VIB of the periodic table. The electronic configuration of the chromium atom is written as 1s 2 2s 2 2p 6 3s 2 3p 6 3d 5 4s 1, i.e. in the case of chromium, as well as in the case of the copper atom, the so-called “electron leakage” is observed
The most commonly exhibited oxidation states of chromium are +2, +3 and +6. They should be remembered, and within the framework of the Unified State Examination program in chemistry, it can be assumed that chromium has no other oxidation states.
Under normal conditions, chromium is resistant to corrosion in both air and water.
Interaction with non-metals
with oxygen
Heated to a temperature of more than 600 o C, powdered chromium metal burns in pure oxygen forming chromium (III) oxide:
4Cr + 3O2 = o t=> 2Cr 2 O 3
with halogens
Chromium reacts with chlorine and fluorine at lower temperatures than with oxygen (250 and 300 o C, respectively):
2Cr + 3F 2 = o t=> 2CrF 3
2Cr + 3Cl2 = o t=> 2CrCl 3
Chromium reacts with bromine at a red-hot temperature (850-900 o C):
2Cr + 3Br 2 = o t=> 2CrBr 3
with nitrogen
Metallic chromium interacts with nitrogen at temperatures above 1000 o C:
2Cr + N 2 = ot=> 2CrN
with sulfur
With sulfur, chromium can form both chromium (II) sulfide and chromium (III) sulfide, which depends on the proportions of sulfur and chromium:
Cr+S= o t=>CrS
2Cr + 3S = o t=> Cr 2 S 3
Chromium does not react with hydrogen.
Interaction with complex substances
Interaction with water
Chromium is a metal of medium activity (located in the activity series of metals between aluminum and hydrogen). This means that the reaction takes place between red-hot chromium and superheated water vapor:
2Cr + 3H2O = o t=> Cr 2 O 3 + 3H 2
Interaction with acids
Chromium under normal conditions is passivated by concentrated sulfuric and nitric acids, however, it dissolves in them upon boiling, while oxidizing to the oxidation state +3:
Cr + 6HNO 3(conc.) = t o=> Cr(NO 3) 3 + 3NO 2 + 3H 2 O
2Cr + 6H 2 SO 4(conc) = t o=> Cr 2 (SO 4) 3 + 3SO 2 + 6H 2 O
In the case of dilute nitric acid, the main product of nitrogen reduction is the simple substance N 2:
10Cr + 36HNO 3(dil) = 10Cr(NO 3) 3 + 3N 2 + 18H 2 O
Chromium is located in the activity series to the left of hydrogen, which means that it is capable of releasing H2 from solutions of non-oxidizing acids. During such reactions, in the absence of access to atmospheric oxygen, chromium (II) salts are formed:
Cr + 2HCl = CrCl 2 + H 2
Cr + H 2 SO 4 (diluted) = CrSO 4 + H 2
When the reaction is carried out in open air, divalent chromium is instantly oxidized by the oxygen contained in the air to the oxidation state +3. In this case, for example, the equation with hydrochloric acid will take the form:
4Cr + 12HCl + 3O 2 = 4CrCl 3 + 6H 2 O
When metallic chromium is fused with strong oxidizing agents in the presence of alkalis, chromium is oxidized to the +6 oxidation state, forming chromates:
Chemical properties of iron
Iron Fe, a chemical element located in group VIIIB and having serial number 26 in the periodic table. The distribution of electrons in the iron atom is as follows: 26 Fe1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 4s 2, that is, iron belongs to the d-elements, since the d-sublevel is filled in its case. It is most characterized by two oxidation states +2 and +3. FeO oxide and Fe(OH) 2 hydroxide have predominant basic properties, while Fe 2 O 3 oxide and Fe(OH) 3 hydroxide have noticeably amphoteric properties. Thus, iron oxide and hydroxide (lll) dissolve to some extent when boiled in concentrated solutions of alkalis, and also react with anhydrous alkalis during fusion. It should be noted that the oxidation state of iron +2 is very unstable, and easily passes into the oxidation state +3. Also known are iron compounds in a rare oxidation state +6 - ferrates, salts of the non-existent “iron acid” H 2 FeO 4. These compounds are relatively stable only in the solid state or in strongly alkaline solutions. If the alkalinity of the environment is insufficient, ferrates quickly oxidize even water, releasing oxygen from it.
Interaction with simple substances
With oxygen
When burned in pure oxygen, iron forms the so-called iron scale, having the formula Fe 3 O 4 and actually representing a mixed oxide, the composition of which can be conventionally represented by the formula FeO∙Fe 2 O 3. The combustion reaction of iron has the form:
3Fe + 2O 2 = t o=> Fe 3 O 4
With sulfur
When heated, iron reacts with sulfur to form ferrous sulfide:
Fe + S = t o=>FeS
Or with excess sulfur iron disulfide:
Fe + 2S = t o=>FeS 2
With halogens
Metallic iron is oxidized by all halogens except iodine to the +3 oxidation state, forming iron halides (lll):
2Fe + 3F 2 = t o=> 2FeF 3 – iron fluoride (lll)
2Fe + 3Cl 2 = t o=> 2FeCl 3 – ferric chloride (lll)
Iodine, as the weakest oxidizing agent among the halogens, oxidizes iron only to the oxidation state +2:
Fe + I 2 = t o=> FeI 2 – iron iodide (ll)
It should be noted that ferric iron compounds easily oxidize iodide ions in an aqueous solution to free iodine I 2 while being reduced to the oxidation state +2. Examples of similar reactions from the FIPI bank:
2FeCl 3 + 2KI = 2FeCl 2 + I 2 + 2KCl
2Fe(OH) 3 + 6HI = 2FeI 2 + I 2 + 6H 2 O
Fe 2 O 3 + 6HI = 2FeI 2 + I 2 + 3H 2 O
With hydrogen
Iron does not react with hydrogen (only alkali metals and alkaline earth metals react with hydrogen from metals):
Interaction with complex substances
Interaction with acids
With non-oxidizing acids
Since iron is located in the activity series to the left of hydrogen, this means that it is capable of displacing hydrogen from non-oxidizing acids (almost all acids except H 2 SO 4 (conc.) and HNO 3 of any concentration):
Fe + H 2 SO 4 (diluted) = FeSO 4 + H 2
Fe + 2HCl = FeCl 2 + H 2
You need to pay attention to such a trick in the Unified State Examination tasks as a question on the topic to what degree of oxidation iron will oxidize when exposed to dilute and concentrated hydrochloric acid. The correct answer is up to +2 in both cases.
The trap here lies in the intuitive expectation of a deeper oxidation of iron (to d.o. +3) in the case of its interaction with concentrated hydrochloric acid.
Interaction with oxidizing acids
Under normal conditions, iron does not react with concentrated sulfuric and nitric acids due to passivation. However, it reacts with them when boiled:
2Fe + 6H 2 SO 4 = o t=> Fe 2 (SO 4) 3 + 3SO 2 + 6H 2 O
Fe + 6HNO3 = o t=> Fe(NO 3) 3 + 3NO 2 + 3H 2 O
Please note that dilute sulfuric acid oxidizes iron to an oxidation state of +2, and concentrated sulfuric acid to +3.
Corrosion (rusting) of iron
In humid air, iron very quickly rusts:
4Fe + 6H 2 O + 3O 2 = 4Fe(OH) 3
Iron does not react with water in the absence of oxygen, either under normal conditions or when boiled. The reaction with water occurs only at temperatures above red heat (>800 o C). those..
In D.I. Mendeleev’s periodic system of elements, copper is located in group I of the 4th period, its serial number is 29. Atomic mass is 63.54. As an element of the first group, copper is monovalent. In this state, it is widely represented in ore minerals, mattes, slags and other products of pyrometallurgy. In the products of their oxidation in nature and in technological processes, the divalent state is more stable.
The melting point of copper is 1083 0 C. The boiling point is 2325 0 C.
Copper is a soft, viscous and malleable metal of red color, easy to machine. Easily rolled into thin sheets and drawn into wire.
The most important property is electrical conductivity (second only to silver). Impurities reduce electrical conductivity, so high-purity copper is used in electrical engineering.
Copper also has high thermal conductivity.
Chemically, copper is inactive, although it can directly combine with oxygen, sulfur, halogens and some other elements.
At normal temperatures and dry air, copper remains inert, but in humid air containing CO 2, copper oxidizes and becomes covered with a protective film of basic carbonate CuCO 3 ·Cu(OH) 2, which is a toxic substance.
Copper does not dissolve in solutions of hydrochloric and sulfuric acids in the absence of an oxidizing agent. In acids that are also oxidizing agents (nitric or hot concentrated sulfuric acid), copper dissolves easily.
At high temperatures in pyrometallurgical processes, stable copper compounds are Cu 2 O and Cu 2 S.
Copper and its sulfide Cu 2 S are good collectors (solvents) of gold and silver, which makes their high associated recovery possible in copper production.
An important property of copper is to form alloys with other metals. These are bronze (Cu + Sn), brass (Cu + Zn) and copper-nickel alloys.
In modern bronzes, aluminum, silicon, beryllium, and lead are used as additives. These bronzes are used for the manufacture of critical parts and cast products.
For example, beryllium bronzes (2% Be) are superior in mechanical properties to many types of steel and have good electrical conductivity. Aluminum bronzes (5-10% Al) are very durable and are used in the manufacture of aircraft engines.
In addition to zinc, aluminum, iron, silicon, and nickel are added to special brasses. Brass is used to make radiators, pipes, flexible hoses, cartridge cases, and art products.
Of the copper-nickel alloys, the most famous are cupronickel (used in shipbuilding, as it is resistant to sea water) and nickel silver - resistant to solutions of salts and organic acids (medical instruments are made).
About 50% of all copper is used by the electrical industry. Copper is also used in mechanical engineering, rocketry, in the production of building materials, in transport, the chemical industry, and agriculture.
1.3 Raw materials for copper production
Clark copper, i.e. its content in the earth's crust is 0.01%. However, it forms numerous deposits. Copper is characterized by the presence of all 4 types of ores in nature. However, the main copper raw materials are sulfide ores. Currently, 85-90% of all primary copper is smelted from sulfide ores.
In Russia, copper ores are mined in the Urals - Kirovgrad, Krasnouralsk, Mednogorsk, Gai, etc., in the Arctic - on the Kola Peninsula and Taimyr.
The sources of copper are ores, their enrichment products - concentrates - and secondary raw materials. Recycled raw materials currently account for about 40% of total copper output.
Copper ores are almost entirely polymetallic. There are no monometallic ores of copper in nature. About 30 elements are valuable companions of copper in ore raw materials. The most important of them are: zinc, lead, nickel, cobalt, gold, silver, platinum group metals, sulfur, selenium, tellurium, cadmium, germanium, rhenium, indium, thallium, molybdenum, iron.
More than 250 copper minerals are known. Most of them are rare. A small group of minerals, the composition of which is given in Table 2, is of greatest industrial importance.
Table 2 - Industrial copper minerals
|
chemical | ||
|
Sulfide minerals |
||
|
chalcopyrite | ||
|
covelline | ||
|
chalcocite | ||
|
Oxidizedminerals |
||
|
CuCO 3 Cu(OH) 2 | ||
|
CuCO 3 2Cu(OH) 2 | ||
|
chrysocolla |
CuSiO 3 2H 2 O | |
|
native copper |
Cu, Ag, Au, Fe, Bi, etc. | |
Most copper ores are currently mined by open-pit mining. In Russia, the share of underground mining accounts for about 30%.
In modern practice, ores are usually developed with a copper content of 0.8-1.5%, sometimes higher. But for large deposits of disseminated ores, the minimum copper content suitable for development is 0.4-0.5%. If the rock contains less than the specified amount of copper, its processing is unprofitable.
The value of copper ores increases significantly due to the presence of noble metals and a number of rare metals - selenium, tellurium, rhenium, bismuth, etc.
Due to the low copper content in the ore and the complex nature of the ores, the raw materials are preliminarily subjected to flotation concentration. When beneficiating copper ores, the main product is copper concentrates containing up to 55% Cu (usually 10-30%). Pyrite concentrates and concentrates of other non-ferrous metals, such as zinc, are also obtained. Flotation concentrates are fine powders with particles of 74 microns and a moisture content of 8-10%.
Copper ores and concentrates have the same mineralogical composition and differ only in the quantitative relationships between various minerals. The physical and chemical bases of their metallurgical processing are exactly the same.
The ancient Greeks called this element chalcos, in Latin it is called cuprum (Cu) or aes, and medieval alchemists called this chemical element nothing more than Mars or Venus. Humanity has long been acquainted with copper due to the fact that in natural conditions it could be found in the form of nuggets, often having very impressive sizes.
The easy reduceability of carbonates and oxides of this element contributed to the fact that, according to many researchers, our ancient ancestors learned to reduce it from ore before all other metals.
At first, copper rocks were simply heated over an open fire and then cooled sharply. This led to their cracking, which made it possible to restore the metal.
Having mastered such a simple technology, man began to gradually develop it. People learned to blow air into fires using bellows and pipes, then they came up with the idea of installing walls around the fire. Eventually, the first shaft furnace was constructed.
Numerous archaeological excavations have made it possible to establish a unique fact - the simplest copper products existed already in the 10th millennium BC! And copper began to be mined and used more actively after 8–10 thousand years. Since then, humanity has been using this chemical element, unique in many respects (density, specific gravity, magnetic characteristics, etc.), for its needs.
These days, copper nuggets are extremely rare. Copper is extracted from various sources, among which are the following:
- bornite (it contains cuprum up to 65%);
- copper luster (also known as chalcocine) with a copper content of up to 80%;
- copper pyrite (in other words, chalcoperite), containing about 30% of the chemical element of interest to us;
- covellite (it contains up to 64% Cu).
Cuprum is also extracted from malachite, cuprite, other oxide ores and almost 20 minerals containing it in varying quantities.
2
In its simplest form, the element described is a metal of a pinkish-red hue, characterized by high ductility. Natural cuprum includes two nuclides with a stable structure.
The radius of a positively charged copper ion has the following values:
- with a coordination index of 6 – up to 0.091 nm;
- with indicator 2 – up to 0.060 nm.
And the neutral atom of the element is characterized by a radius of 0.128 nm and an electron affinity of 1.8 eV. During sequential ionization, the atom has values from 7.726 to 82.7 eV.
Cuprum is a transition metal, so it has variable oxidation states and a low electronegativity index (1.9 units on the Pauling scale). (coefficient) is equal to 394 W/(m*K) at a temperature range from 20 to 100 °C. The electrical conductivity of copper (specific indicator) is a maximum of 58, a minimum of 55.5 MS/m. Only silver has a higher value; the electrical conductivity of other metals, including aluminum, is lower.
Copper cannot displace hydrogen from acids and water, since in the standard potential series it is to the right of hydrogen. The described metal is characterized by a face-centered cubic lattice with a size of 0.36150 nm. Copper boils at a temperature of 2657 degrees, melts at a temperature of just over 1083 degrees, and its density is 8.92 grams / cubic centimeter (for comparison, the density of aluminum is 2.7).
Other mechanical properties of copper and important physical indicators:
- pressure at 1628 °C – 1 mm Hg. Art.;
- thermal expansion value (linear) – 0.00000017 units;
- when stretching, a tensile strength of 22 kgf/mm2 is achieved;
- copper hardness – 35 kgf/mm2 (Brinell scale);
- specific gravity – 8.94 g/cm3;
- modulus of elasticity – 132000 Mn/m2;
- elongation (relative) – 60%.
The magnetic properties of copper are somewhat unique. The element is completely diamagnetic, its magnetic atomic susceptibility is only 0.00000527 units. The magnetic characteristics of copper (as well as all its physical parameters - weight, density, etc.) determine the demand for the element for the manufacture of electrical products. Aluminum has approximately the same characteristics, so they and the described metal form a “sweet couple” used for the production of conductor parts, wires, and cables.
It is almost impossible to change many mechanical properties of copper (the same magnetic properties, for example), but the tensile strength of the element in question can be improved by cold hardening. In this case, it will approximately double (up to 420–450 MN/m2).
3
Cuprum in the periodic system is included in the group of noble metals (IB), it is in the fourth period, has an atomic number of 29, and has a tendency to form complexes. The chemical characteristics of copper are no less important than its magnetic, mechanical and physical characteristics, be it its weight, density or other value. Therefore, we will talk about them in detail.
The chemical activity of cuprum is low. Copper in a dry atmosphere changes insignificantly (one might even say that it almost does not change). But with increasing humidity and the presence of carbon dioxide in the environment, a greenish film usually forms on its surface. It contains CuCO3 and Cu(OH)2, as well as various copper sulphide compounds. The latter are formed due to the fact that there is almost always a certain amount of hydrogen sulfide and sulfur dioxide in the air. This greenish film is called patina. It protects the metal from destruction.
If copper is heated in air, oxidation processes on its surface will begin. At temperatures from 375 to 1100 degrees, two-layer scale is formed as a result of oxidation, and at temperatures up to 375 degrees, copper oxide is formed. At ordinary temperatures, a combination of Cu with wet chlorine is usually observed (the result of this reaction is the appearance of chloride).
Copper also interacts quite easily with other elements of the halogen group. It ignites in sulfur vapor; it also has a high level of affinity for selenium. But Cu does not combine with carbon, nitrogen and hydrogen even at elevated temperatures. When copper oxide comes into contact with sulfuric acid (diluted), copper sulfate and pure copper are obtained; with hydroiodic and hydrobromic acids, copper iodide and bromide are obtained, respectively.
If the oxide is combined with one or another alkali, the result of the chemical reaction will be the appearance of cuprate. But the most famous reducing agents (carbon monoxide, ammonia, methane and others) are able to restore cuprum to a free state.
Of practical interest is the ability of this metal to react with iron salts (in the form of a solution). In this case, the reduction of iron and the transition of Cu into solution are recorded. This reaction is used to remove the deposited layer of copper from decorative products.
In mono- and divalent forms, copper is capable of creating complex compounds with a high level of stability. Such compounds include ammonia mixtures (they are of interest to industrial enterprises) and double salts.
4
The main area of application of aluminum and copper is known, perhaps, to everyone. They are used to make a variety of cables, including power cables. This is facilitated by the low resistance of aluminum and cuprum and their special magnetic capabilities. In the windings of electric drives and in transformers (power), copper wires are widely used, which are characterized by the unique purity of copper, which is the raw material for their production. If you add only 0.02 percent aluminum to such pure raw materials, the electrical conductivity of the product will decrease by 8–10 percent.
Cu, which has high density and strength, as well as low weight, is perfectly amenable to machining. This allows us to produce excellent copper pipes that demonstrate their high performance characteristics in gas, heating, and water supply systems. In many European countries, copper pipes are used in the vast majority of cases for the arrangement of internal utility networks of residential and administrative buildings.
We have said a lot about the electrical conductivity of aluminum and copper. Let's not forget about the excellent thermal conductivity of the latter. This characteristic makes it possible to use copper in the following structures:
- in heat pipes;
- in coolers of personal computers;
- in heating systems and air cooling systems;
- in heat exchangers and many other devices that remove heat.
The density and light weight of copper materials and alloys have also led to their widespread use in architecture.
5
It is clear that the density of copper, its weight and all kinds of chemical and magnetic indicators, by and large, are of little interest to the average person. But many people want to know the healing properties of copper.
The ancient Indians used copper to treat the eyes and various skin ailments. The ancient Greeks used copper plates to cure ulcers, severe swelling, bruises and contusions, as well as more serious diseases (inflammation of the tonsils, congenital and acquired deafness). And in the east, red copper powder, dissolved in water, was used to restore broken bones in the legs and arms.
The healing properties of copper were well known to Russians. Our ancestors used this unique metal to cure cholera, epilepsy, polyarthritis and radiculitis. Currently, copper plates are usually used for treatment, which are applied to special points on the human body. The healing properties of copper in such therapy are manifested in the following:
- the protective potential of the human body increases;
- infectious diseases are not dangerous for those who are treated with copper;
- There is a decrease in pain and relief from inflammation.
People studied the properties of copper, which occurs in nature in the form of fairly large nuggets, back in ancient times, when dishes, weapons, jewelry, and various household products were made from this metal and its alloys. The active use of this metal for many years is due not only to its special properties, but also to the ease of processing. Copper, which is present in the ore in the form of carbonates and oxides, is quite easily reduced, which is what our ancient ancestors learned to do.
Initially, the process of recovering this metal looked very primitive: copper ore was simply heated over fires and then subjected to sudden cooling, which led to cracking of pieces of ore, from which copper could already be extracted. Further development of this technology led to the fact that air began to be blown into the fires: this increased the heating temperature of the ore. Then the ore began to be heated in special structures, which became the first prototypes of shaft furnaces.
The fact that copper has been used by mankind since ancient times is evidenced by archaeological finds, as a result of which products made from this metal were found. Historians have established that the first copper products appeared already in the 10th millennium BC, and it began to be most actively mined, processed and used 8–10 thousand years later. Naturally, the prerequisites for such active use of this metal were not only the relative ease of its extraction from ore, but also its unique properties: specific gravity, density, magnetic properties, electrical and specific conductivity, etc.
Nowadays, it is already difficult to find in the form of nuggets; it is usually mined from ore, which is divided into the following types.
- Bornite - this ore can contain copper in amounts up to 65%.
- Chalcocite, also called copper luster. Such ore can contain up to 80% copper.
- Copper pyrite, also called chalcopyrite (content up to 30%).
- Covelline (content up to 64%).
Copper can also be extracted from many other minerals (malachite, cuprite, etc.). They contain it in different quantities.
Physical properties
Copper in its pure form is a metal whose color can vary from pink to red.
The radius of copper ions having a positive charge can take the following values:
- if the coordination index corresponds to 6 - up to 0.091 nm;
- if this indicator corresponds to 2 - up to 0.06 nm.
The radius of the copper atom is 0.128 nm, and it is also characterized by an electron affinity of 1.8 eV. When an atom is ionized, this value can take a value from 7.726 to 82.7 eV.
Copper is a transition metal with an electronegativity value of 1.9 on the Pauling scale. In addition, its oxidation state can take on different values. At temperatures ranging from 20 to 100 degrees, its thermal conductivity is 394 W/m*K. The electrical conductivity of copper, which is surpassed only by silver, is in the range of 55.5–58 MS/m.
Since copper in the potential series is to the right of hydrogen, it cannot displace this element from water and various acids. Its crystal lattice has a cubic face-centered type, its value is 0.36150 nm. Copper melts at a temperature of 1083 degrees, and its boiling point is 26570. The physical properties of copper are also determined by its density, which is 8.92 g/cm3.
Of its mechanical properties and physical indicators, the following are also worth noting:
- thermal linear expansion - 0.00000017 units;
- the tensile strength to which copper products correspond is 22 kgf/mm2;
- the hardness of copper on the Brinell scale corresponds to a value of 35 kgf/mm2;
- specific gravity 8.94 g/cm3;
- elastic modulus is 132000 Mn/m2;
- the elongation value is 60%.
The magnetic properties of this metal, which is completely diamagnetic, can be considered completely unique. It is these properties, along with physical parameters: specific gravity, specific conductivity and others, that fully explain the wide demand for this metal in the production of electrical products. Aluminum has similar properties, which is also successfully used in the production of various electrical products: wires, cables, etc.
The main part of the characteristics that copper has is almost impossible to change, with the exception of its tensile strength. This property can be improved almost twice (up to 420–450 MN/m2) if a technological operation such as hardening is carried out.
Chemical properties
The chemical properties of copper are determined by its position in the periodic table, where it has serial number 29 and is located in the fourth period. What is noteworthy is that it is in the same group with noble metals. This once again confirms the uniqueness of its chemical properties, which should be discussed in more detail.
In conditions of low humidity, copper exhibits virtually no chemical activity. Everything changes if the product is placed in conditions characterized by high humidity and high carbon dioxide content. Under such conditions, active oxidation of copper begins: a greenish film consisting of CuCO3, Cu(OH)2 and various sulfur compounds is formed on its surface. This film, called patina, performs the important function of protecting the metal from further destruction.
Oxidation begins to actively occur when the product is heated. If the metal is heated to a temperature of 375 degrees, then copper oxide is formed on its surface, if higher (375-1100 degrees) then two-layer scale.
Copper reacts quite easily with elements that are part of the halogen group. If a metal is placed in sulfur vapor, it will ignite. It also shows a high degree of affinity for selenium. Copper does not react with nitrogen, carbon and hydrogen even at high temperatures.
The interaction of copper oxide with various substances deserves attention. Thus, when it reacts with sulfuric acid, sulfate and pure copper are formed, with hydrobromic and hydroiodic acid - copper bromide and iodide.
The reactions of copper oxide with alkalis, which result in the formation of cuprate, look different. The production of copper, in which the metal is reduced to a free state, is carried out using carbon monoxide, ammonia, methane and other materials.
Copper, when interacting with a solution of iron salts, goes into solution, and the iron is reduced. This reaction is used to remove the deposited copper layer from various products.
Mono- and divalent copper is capable of creating complex compounds that are highly stable. Such compounds are double copper salts and ammonia mixtures. Both have found wide application in various industries.
Applications of copper
The use of copper, as well as aluminum, which is most similar in properties to it, is well known - in the production of cable products. Copper wires and cables are characterized by low electrical resistance and special magnetic properties. For the production of cable products, types of copper characterized by high purity are used. If even a small amount of foreign metal impurities is added to its composition, for example, only 0.02% aluminum, then the electrical conductivity of the original metal will decrease by 8–10%.
Low and its high strength, as well as the ability to lend itself to various types of mechanical processing - these are the properties that make it possible to produce pipes from it that are successfully used for transporting gas, hot and cold water, and steam. It is no coincidence that these pipes are used as part of the engineering communications of residential and administrative buildings in most European countries.
Copper, in addition to exceptionally high electrical conductivity, is distinguished by its ability to conduct heat well. Thanks to this property, it is successfully used as part of the following systems.