Views: 0 Author: Site Editor Publish Time: 2022-08-03 Origin: Site
It is said that in ancient Rome, one day, a stranger went to visit the Roman emperor Tiberius and presented a metal cup. The cup glittered like silver, but the weight was very light. It is the new metal that this man extracted from clay. But the emperor expressed his gratitude on the surface, but he was afraid that this dazzling new metal would devalue his gold and silver treasures, so he ordered the inventor to be beheaded. Since then, no one has ever moved the idea of refining this "dangerous metal". This new metal is now very familiar with aluminum. The word aluminum is derived from the ancient Roman alum.
The French emperor Napoleon III, in order to show his wealth and dignity, ordered officials to make himself a crown more valuable than gold - aluminum crown. He wore an aluminum crown and accepted the worship of officials with great dignity, which was once a blockbuster news. When Napoleon III held a grand banquet, only he used a set of aluminum tableware, while others could only use gold and silver tableware. Even in the chemical world, aluminum is regarded as the most valuable. In order to commend Mendeleev's outstanding contribution to chemistry, the Royal Society of England spared no expense in making an aluminum cup and presented it to Mendeleev. Russian writer Chernychevsky once wrote in his novel how to do: one day, aluminum will replace wood, and may even replace stone. Look, how extravagant it is. Aluminum is everywhere.
We all know that aluminum is the most abundant metal in the earth's crust, accounting for 7.45% of the total mass of the whole earth's crust, second only to oxygen and silicon, ranking first among metal elements, 1.5 times the iron content ranking second, and nearly 4 times that of copper.
Silver white shiny metal, density 2.702 g / cubic centimeter, melting point 660.37 ℃, boiling point 2467 ℃. It has good thermal conductivity, conductivity and ductility. Valence +3, ionization energy 5.986 electron volts. Aluminum is known as an active metal element, but its surface will form a dense oxide film in the air, which makes it unable to continue to interact with oxygen and water. It can react with oxygen at high temperature and release a lot of heat. With this high reaction heat, aluminum can replace metal from other oxides (thermite method).
For example: 8al+3fe ₃ o ₄ =4al ₃ o ₃ +9fe +795 kcal. (magnesium is required as the ignitor)
At high temperature, aluminum also reacts with nonmetals, and can also dissolve in acids or bases to release hydrogen. It has no effect on water, sulfide, concentrated sulfuric acid, acetic acid of any concentration, and all organic acids.
Aluminum exists in various rocks or ores in the form of compound, such as feldspar, mica, kaolinite, bauxite, alum, etc. The oxide containing aluminum is produced by CO melting and electrolysis with cryolite (3naf · ALF ₃).
Reaction process of extracting aluminum from bauxite
① Dissolution: dissolve bauxite in NaOH (AQ)
Al Ψ o ₃ + 2naoh ===== 2naalo Э (sodium aluminate) + H Э o
② Filtration: remove the residue, such as ferrous oxide (fe‹o ₃), sodium aluminosilicate, etc
③ Acidification: inject excessive CO 2 into the filtrate
NaAlO₂+ CO₂+ 2H₂O ==== Al(OH)₃↓+ NaHCO₃
④ Filter and burn Al (OH) ₃
2Al (OH) ₃ = = high temperature = = Al Э o ₃ + 3H Э o
Note: in order to reduce the melting temperature of alumina during electrolysis, cryolite (3naf · ALF ₃) is added to Al Ψ o ₃
⑤ Electrolysis: 2Al Ψ o ₃ (I) = = energized = = 4Al + 3O Ψ ↑
Note: ALCL ₃ is not fused by electrolysis. Reason: ALCL ₃ is a covalent compound, and its molten state is not conductive.
However, due to its strong oxidizing power, aluminum is not easy to be reduced, so it was found later.
After Volta, an Italian physicist, created the battery in 1800, David, a British chemist, and bezirius, a Swedish chemist, both tried to separate aluminum from bauxite by electric current between 1808 and 1810, but failed. Bezirius gave the metal, which had not been obtained, a name alumien. This is from Latin alumen. In medieval Europe, the term "convergent alum" refers to the mordant used in dyeing cotton fabrics. It is from this that the later Latin name aluminum and the element symbol al came.
In 1825, the Danish chemist osder published the process of experimental preparation of aluminum. In 1827, the German chemist wuller repeated osder's experiment and constantly improved the method of making aluminum. In 1854, German chemist de vill reduced aluminum chloride with sodium instead of potassium to produce ingot aluminum.
Element symbol: al English Name: Aluminum Chinese Name: Aluminum
Relative atomic mass: 26.9815 common valence: +3 electronegativity: 1.61
Peripheral electron arrangement: 3s2 3P1 extranuclear electron arrangement: 2,8,3
Isotope and radiation: al-26[730000y] *al-27 al-28[2.3m]
Electron affinity and energy: 48 kJ · mol-1
First ionization energy: 577.6 kJ · mol-1 second ionization energy: 1817 kJ · mol-1 third ionization energy: 2745 kJ · mol-1
Density of single substance: 2.702 g/cm3 melting point of single substance: 660.37 ℃ boiling point of single substance: 2467 ℃
Atomic radius: 1.82 angstrom ionic radius: 0.51 (+3) angstrom covalent radius: 1.18 angstrom
Common compounds: Al Э o ₃ ALCL ₃ al Э s ₃ NaAlO Э al Э (so ₄) ₃ Al (OH) ₃
Atomic weight 26.981539. In 1825, Danish scientist Auster mixed anhydrous aluminum trichloride with potassium amalgam, and evaporated the mercury to obtain aluminum; In 1854, Deville reduced the molten salt of sodium chloride and aluminum chloride with metal sodium to produce metal aluminum, which was displayed at the Paris Exposition in 1855; In 1886, hall and ERU invented the molten salt method of electrolytic aluminum oxide and cryolite respectively, making aluminum a practical metal. The content of aluminum in the earth's crust is 8%, second only to oxygen and silicon. It is widely distributed in rocks, soil, animals and plants.
Aluminum is a silver white light metal, with a melting point of 660.37 ° C, a boiling point of 2467 ° C, and a density of 2.702 g / cm ³. Aluminum is face centered cubic structure, which has good conductivity and thermal conductivity; Pure aluminum is soft.
Aluminum is an active metal. In dry air, a dense oxide film about 50 Angstroms thick is immediately formed on the surface of aluminum, so that aluminum will not be further oxidized and can resist water; However, aluminum powder is very easy to burn when mixed with air; Molten aluminum can react violently with water; Many metal oxides can be reduced to corresponding metals at high temperature; Aluminum is amphoteric, which is easily soluble in strong alkali and dilute acid.