Cuprum (Cu) is among the low-activity metals. It is characterized by the formation of chemical compounds with oxidation states of +1 and +2. So, for example, two oxides, which are a compound of two elements Cu and oxygen O: with an oxidation state of +1 - copper oxide Cu2O and an oxidation state of +2 - copper oxide CuO. Despite the fact that they consist of the same chemical elements, but each of them has its own special characteristics. In cold weather, the metal interacts very weakly with atmospheric oxygen, becoming covered by a film of copper oxide, which prevents further oxidation of cuprum. When heated, this simple substance with serial number 29 in the periodic table is completely oxidized. In this case, copper (II) oxide is also formed: 2Cu + O2 → 2CuO.
Nitrous oxide is a brownish-red solid with a molar mass of 143.1 g / mol. The compound has a melting point of 1235 ° C, a boiling point of 1800 ° C. It is not soluble in water, but soluble in acids. Copper (I) oxide is diluted in ammonia solution (concentrated), and a colorless complex [Cu (NH3) 2] + is formed, which is easily oxidized in air to the ammonia complex of the blue-violet color [Cu (NH3) 4 (H2O) 2] 2+, soluble in hydrochloric acid to form CuCl2. In the history of semiconductor physics, Cu2O is one of the most studied materials.
Copper oxide (I), also known as hemioxide, has basic properties. It can be obtained by metal oxidation: 4Cu + O2 → 2 Cu2O. Impurities, such as water and acids, affect the speed of this process, as well as further oxidation to divalent oxide. Copper oxide can dissolve in sulfuric acid, and a pure metal and salt are formed: H2SO4 + Cu2O → Cu + CuSO4 + H2O. According to a similar scheme, the oxide interacts with the oxidation state of the metal +1 with other oxygen-containing acids. In the interaction of hemioxide with halogen-containing acids, monovalent metal salts are formed: 2HCl + Cu2O → 2CuCl + H2O.
Copper (I) oxide is found in nature in the form of red ore (this is an outdated name, along with ruby Cu), called the mineral "Cuprite". His education takes a long time. It can be obtained artificially at high temperatures or under high oxygen pressure. Hemoxide is usually used as a fungicide, as a pigment, as an antifouling agent in underwater or marine paint, and is also used as a catalyst.
However, exposure to this substance with the chemical formula Cu2O on the body can be dangerous. If inhaled, causes shortness of breath, cough, and ulceration and perforation of the airways. If ingested, it irritates the gastrointestinal tract, which is accompanied by vomiting, pain and diarrhea.
Higher copper oxide in appearance is a powder from brown to black. In nature, in its pure form is found as the mineral "Tenorite". Its melting point is 1326 ° C, the boiling point is 2000 ° C. It is insoluble in water, alcohol, ammonium hydroxide, a solution of ammonium carbonate. Soluble in aqueous solutions of ammonium chloride and potassium cyanide. This black solid can be obtained by heating Cu in air. However, in this case, Cu oxide is also formed. Obtaining copper oxide CuO is possible by heating the compounds:
copper (II) nitrate 2Cu (NO3) 2 → 4 NO2 + O2 + 2CuO;
copper (II) hydroxide Cu (OH) 2 → H2O + CuO;
copper (II) carbonate CuCO3 → CO2 + CuO.
Cuprum (II) oxide is the main, therefore, it dissolves in mineral acids (hydrochloric, sulfuric and nitric) to obtain the corresponding salt of divalent Cu:
2HCl + CuO → CuCl2 + H2O;
H2SO4 + CuO → CuSO4 + H2O;
2HNO3 + CuO → Cu (NO3) 2 + H2O.
Copper (II) oxide reacts with concentrated alkali to form a salt: 2 KOH + CuO + H2O → K2 [Cu (OH) 4].
The oxide can also be reduced to metallic Cu by reaction with hydrogen or carbon monoxide :
H2 + CuO → Cu + H2O;
CO + CuO → Cu + CO2.
Copper (II) oxide is used in ceramics (as a pigment) to produce glaze (blue, green and red, and sometimes pink, gray or black). It is also used as a dietary supplement in animals to reduce cuprum deficiency in the body. This is an abrasive material that is necessary for polishing optical equipment. It is used to produce dry batteries, to produce other Cu salts. The CuO compound is also used in the welding of copper alloys.
Exposure to the chemical compound CuO can also be hazardous to the human body. Inhalation causes lung irritation. Copper (II) oxide can cause metal vapor fever (MFF). Cu oxide provokes a discoloration of the skin, and vision problems may occur. When ingested, like hemioxide, it leads to poisoning, which is accompanied by symptoms in the form of vomiting and pain.