The sodium hydroxide It is an inorganic compound whose chemical formula is NaOH and consists of a very strong metallic base or alkali. A 5% solution of it in water has a pH close to 14.
It is a very hygroscopic white solid that can also absorb carbon dioxide from the air to form sodium carbonate. It comes commercially in plastic bottles as pills, which cannot be exposed for too long to the air, nor should they be manipulated with spatulas.
Sodium hydroxide can be synthesized by reacting calcium hydroxide with sodium carbonate. Currently however, it is fundamentally synthesized by electrolysis of brine, and is a by-product of the production of chlorine gas.
Given the high basicity of NaOH, it has numerous uses and applications, such as the production of paper, soaps, detergents, dyes, etc. It is also used in household cleaning, water treatment, aluminum processing, medicine manufacturing, etc .; and above all, it is a secondary pattern par excellence.
Sodium hydroxide is very corrosive, being capable of causing irritation and burns to the skin and eyes. By inhaling its dust, it can cause pulmonary edema. Meanwhile, its ingestion can cause such serious damage to the digestive tract that it can lead to death..
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The upper image shows the ions that make up NaOH. The Na cation+ is represented by the purple sphere, while the hydroxyl anion (hydroxide or hydroxyl) OH- by the red and white sphere. Both Na ions+ and OH- interact with each other through the electrostatic attraction of their opposite charges.
Such interactions are nondirectional, so the attractions of an ion pair Na+Oh- it can affect those of others at a certain distance. The result is that the Na ions+ repel each other, in the same way that OH-, until defining a crystal of minimum energy where they establish an ordered and periodic structure (crystalline).
Therefore, the orthorhombic crystals of anhydrous NaOH (without water) appear:
The ions remain sufficiently cohesive so that the anhydrous NaOH crystal melts at 323 ºC (as long as there is no humidity in the environment).
Both the Na+ like OH- They are ions that water molecules easily solvate (hydrate). This favors its hydration above the reticular energy of its crystals, which is why NaOH releases a lot of energy when it comes into contact with water..
However, anhydrous crystals can host undissolved water molecules; that is, sodium hydroxide can form numerous hydrates, NaOH nHtwoO. The water molecule may well form a hydrogen bond with the OH- (HOH-OH-), or coordinate with the Na+ (Na+-Ohtwo).
Depending on the molar ratio between NaOH and HtwoOr, monohydrates (NaOHHtwoO), dihydrates (NaOH 2HtwoO), trihemidrates (NaOH 3.5HtwoO), tetrahydrates (NaOH 4HtwoO), heptahydrates (NaOH 7HtwoO), and more.
Each of these hydrates can crystallize from an aqueous solution of NaOH with different mass percentages and at different temperatures. Consequently, NaOH exhibits a complicated water solubility diagram..
In general terms, the crystals of hydrates are less dense and have lower melting points. This is because the water molecules “hinder” the interactions between Na+ and OH-, adding dipole-dipole forces at the sacrifice of ionic attractions.
IUPAC preferred name: sodium hydroxide. Other names: Caustic soda, Ascarite (less common)
39.9971 g / mol
White, serous, or opaque solid or crystals.
323 ºC
1,388 ºC
1,000 g / L at a temperature of 25 ° C. This shows how much it can dissolve in water..
Their aqueous solutions are viscous, with a viscosity value about eighty times that of water, and they release a lot of heat at first. If you have contact with them, they make the skin slippery, due to the saponification of the fatty acids in the skin..
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A 5% w / w solution in water has a pH close to 14
At a wavelength of 580.4 nm: 1,433 at 320 ºC, and 1,421 at 420 ºC.
Containers containing it must be hermetically closed to prevent the formation of sodium carbonate. This is due to its high hygroscopicity, which leads it to absorb moisture from its surroundings and its CO content.two.
When heated to decomposition it emits sodium oxide smoke.
It is not flammable
4.0 cPoise at 350 ºC
175 kJ / mol at 1,388 ºC
74.35 dynes / cm in a 2.72% w / w solution in water at 18 ºC.
Reacts with organic and inorganic mineral acids, creating water and the corresponding salt. In the case of sulfuric acid the reaction is exothermic.
2 NaOH + HtwoSW4 => NatwoSW4 + 2 htwoOR
Reacts with sulfur dioxide, for example, giving a sulfite salt of and water:
2 NaOH + SOtwo => NatwoSW3 + HtwoOR
Its aqueous solutions react with some metals to produce complex sodium salts. For example, its reaction with zinc gives rise to a sodium zincate:
Zn + 2 NaOH + 2 HtwoO => Natwo[Zn (OH)4] + Htwo
Sodium hydroxide is synthesized mainly by two methods: the use of sodium carbonate, initially used, and the electrolysis of sodium chloride, currently in greater industrial use..
Sodium carbonate reacts with calcium hydroxide in a process known as causticisation:
Ca (OH)two + NatwoCO3 => CaCO3 + NaOH
Calcium carbonate precipitates, leaving sodium hydroxide in the supernatant, which is concentrated by evaporation.
Sodium carbonate comes previously from the Solvay process:
2 NaCl + CaCO3 => NatwoCO3 + CaCltwo
The electrolysis of sodium chloride, present in the brine, produces hydrogen gas, chloride gas and sodium hydroxide in aqueous solution:
2 Nacl + 2 HtwoO => Htwo + Cltwo + 2 NaOH
The electrolytic chamber consists of a compartment where the anode (+) is, made of titanium metal, and a place where the brine is placed. This compartment is separated from the cathode compartment (-) by a porous membrane..
The following reaction occurs at the anode:
2 Cl- => Cltwo + 2 e- (oxidation)
Meanwhile, this reaction occurs at the cathode:
2 htwoO + 2 e- => Htwo + Oh- (reduction)
Sodium (Na+) diffuses from the anode compartment to the cathode compartment, through the membrane that separates them, forming sodium hydroxide.
Sodium hydroxide is used to make soaps and detergents used in the home and in business. The combination of sodium hydroxide and chlorine produces chlorine bleach, used in washing white clothes.
It also eliminates the accumulation of fat in the drains, producing its elimination through its conversion into soaps through the saponification process. This allows the elimination of the clogging of the pipes of the homes and other buildings.
Sodium hydroxide is used to make common pain relievers, such as aspirin. Also of drugs with anticoagulant action that block the formation of blood clots and drugs to reduce hypercholesterolemia.
Sodium hydroxide is used in the manufacture of fuel cells that function like batteries to produce electricity for a variety of applications, including transportation. Epoxy resins, manufactured with the intervention of sodium hydroxide, are used in wind turbines.
Sodium hydroxide is used to neutralize the acidity of the water and contribute to the removal of heavy metals from it. It is also used for the production of sodium hypochlorite, a water disinfectant.
Sodium hydroxide is reacted with aluminum sulfate to form aluminum hydroxide: a flocculating agent that is used in water treatment plants to increase the sedimentation of particles, producing their clarification..
Sodium hydroxide is used with sodium sulfide in the treatment of wood to obtain cellulose, in an almost pure form, which forms the basis of paper. It is also used in the recycling of paper, since by helping to separate the ink, it allows it to be used again.
Sodium hydroxide is used in the manufacture of rayon, spandex, explosives, epoxy resins, glass, and ceramics. It is used in the textile industry to make dyes, and process cotton fabrics.
In sugarcane treatment plants, low-temperature sodium hydroxide is used for the production of ethanol from sugarcane bagasse.
Sodium hydroxide is a highly corrosive compound, so it can cause, by contact with the skin, burns, blisters and even permanent scars.
In contact with the eyes, it can cause severe burns, swelling, pain, blurred vision, and in severe cases, it can cause permanent blindness..
Swallowing sodium hydroxide can cause burns to the lips, tongue, throat, esophagus, and stomach. Common symptoms include nausea, vomiting, stomach cramps, and diarrhea..
Although the inhalation of sodium hydroxide is rare, and can only occur due to the presence of dust of the compound in the air or from the formation of a mist that contains it, it produces irritation in the lungs..
In the case of chronic exposure, this can cause pulmonary edema and severe shortness of breath, which constitutes a medical emergency..
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