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Superoxides
In chemistry, a superoxide is a compound that contains the superoxide ion, which has the chemical formula . The systematic name of the anion is dioxide(1−). The reactive oxygen ion superoxide is particularly important as the product of the one-electron reduction of dioxygen , which occurs widely in nature. Molecular oxygen (dioxygen) is a diradical containing two unpaired electrons, and superoxide results from the addition of an electron which fills one of the two degenerate molecular orbitals, leaving a charged ionic species with a single unpaired electron and a net negative charge of −1. Both dioxygen and the superoxide anion are free radicals that exhibit paramagnetism. Superoxide was historically also known as "hyperoxide". Salts Superoxide forms salts with alkali metals and alkaline earth metals. The salts sodium superoxide (), potassium superoxide (), rubidium superoxide () and caesium superoxide () are prepared by the reaction of with the respective al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sodium Superoxide
Sodium superoxide is the inorganic compound with the formula Na O2. This yellow-orange solid is a salt of the superoxide anion. It is an intermediate in the oxidation of sodium by oxygen. Preparation NaO2 is prepared by treating sodium peroxide with oxygen at high pressures: :Na2O2 + O2 → 2 NaO2 It can also be prepared by careful oxygenation of a solution of sodium in cryogenic liquid ammonia: :Na(in NH3) + O2 → NaO2 Although the existence of a sodium oxide higher than peroxide was speculated since 19th century, it was not until 1948 when American chemists were able to definitely synthesize it by the latter method. It is also produced, along with sodium peroxide, when sodium is stored under inappropriate conditions (e.g. in dirty or partially halogenated solvents). Properties The product is paramagnetic, as expected for a salt of the anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydroperoxyl
The hydroperoxyl radical, also known as the hydrogen superoxide, is the protonated form of superoxide with the chemical formula HO2, also written HOO•. This species plays an important role in the atmosphere and as a reactive oxygen species in cell biology. Structure and reactions The molecule has a bent structure. The superoxide anion, , and the hydroperoxyl radical exist in equilibrium in aqueous solution: : + + The p''K''a of HO2 is 4.88. Therefore, about 0.3% of any superoxide present in the cytosol of a typical cell is in the protonated form. It oxidizes nitric oxide to nitrogen dioxide: : + → + Reactive oxygen species in biology Together with its conjugate base superoxide, hydroperoxyl is an important reactive oxygen species. Unlike , which has reducing properties, can act as an oxidant in a number of biologically important reactions, such as the abstraction of hydrogen atoms from tocopherol and polyunstaturated fatty acids in the lipid bilayer. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caesium Superoxide
Caesium superoxide is a chemical compound with the chemical formula . It consists of caesium cations and superoxide anions . It is an orange solid. Preparation Burning caesium in excess oxygen will produce caesium superoxide. : Properties Caesium superoxide's crystal structure is same as calcium carbide. It contains direct oxygen-oxygen bonding. It reacts with water to form hydrogen peroxide and caesium hydroxide. : Heating to approximately 400 °C induces thermal decomposition to caesium peroxide. The standard enthalpy of formation Δ''H''f0 of caesium superoxide is −295 kJ/mol. Caesium superoxide reacts with ozone Ozone () (or trioxygen) is an Inorganic compound, inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , break ... to form caesium ozonide. : References {{oxides Caesium compounds Superoxides ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rubidium Superoxide
Rubidium superoxide or rubidium hyperoxide is a chemical compound with the chemical formula . In terms of oxidation states, the negatively charged superoxide and positively charged rubidium give it a structural formula of . Chemistry It can be created by slowly exposing elemental rubidium to oxygen gas: : Like other alkali metal hyperoxides, crystals can also be grown in liquid ammonia. Between 280 and 360 °C, Rubidium superoxide will decompose, leaving not rubidium sesquioxide (), but rather rubidium peroxide (). : An even more oxygen rich compound, that of rubidium ozonide () can be created using . Properties Roughly speaking, has a crystal structure similar to tetragonal calcium carbide, but is rather distorted due to the Jahn–Teller effect, which makes the crystal structure less symmetrical. is stable in dry air, but is extremely hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorptio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Potassium Superoxide
Potassium superoxide is an inorganic compound with the formula . It is a yellow paramagnetic solid that decomposes in moist air. It is a rare example of a stable salt of the superoxide anion. It is used as a scrubber, dehumidifier, and generator in rebreathers, spacecraft, submarines, and spacesuits. Production and reactions Potassium superoxide is produced by burning molten potassium in an atmosphere of excess oxygen. : The salt consists of and ions, linked by ionic bonding. The O–O distance is 1.28 Å. Reactivity Potassium superoxide is a source of superoxide, which is an oxidant and a nucleophile, depending on its reaction partner. Upon contact with water, it undergoes disproportionation to potassium hydroxide, oxygen, and hydrogen peroxide: : : It reacts with carbon dioxide, releasing oxygen: : : Theoretically, 1 kg of absorbs 0.310 kg of while releasing 0.338 kg of . One mole of absorbs 0.5 moles of and releases 0.75 moles of oxygen. Potass ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lewis Structure
Lewis structuresalso called Lewis dot formulas, Lewis dot structures, electron dot structures, or Lewis electron dot structures (LEDs)are diagrams that show the chemical bond, bonding between atoms of a molecule, as well as the lone pairs of electrons that may exist in the molecule. Introduced by Gilbert N. Lewis in his 1916 article ''The Atom and the Molecule'', a Lewis structure can be drawn for any covalently bonded molecule, as well as complex (chemistry), coordination compounds. Lewis structures extend the concept of the electron dot diagram by adding lines between atoms to represent shared pairs in a chemical bond. Lewis structures show each atom and its position in the structure of the molecule using its chemical symbol. Lines are drawn between atoms that are bonded to one another (pairs of dots can be used instead of lines). Excess electrons that form lone pairs are represented as pairs of dots, and are placed next to the atoms. Although main group elements of the Period ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aqueous Solution
An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, also known as sodium chloride (NaCl), in water would be represented as . The word ''aqueous'' (which comes from ''aqua'') means pertaining to, related to, similar to, or dissolved in, water. As water is an excellent solvent and is also naturally abundant, it is a ubiquitous solvent in chemistry. Since water is frequently used as the solvent in experiments, the word solution refers to an aqueous solution, unless the solvent is specified. A ''non-aqueous solution'' is a solution in which the solvent is a liquid, but is not water. Characteristics Substances that are ''hydrophobic'' ('water-fearing') do not dissolve well in water, whereas those that are '' hydrophilic'' ('water-friendly') do. An example of a hydrophilic substance is sodium chloride. In an aqueous solution the hydrogen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Equilibrium
In a chemical reaction, chemical equilibrium is the state in which both the Reagent, reactants and Product (chemistry), products are present in concentrations which have no further tendency to change with time, so that there is no observable change in the properties of the Thermodynamic system, system. This state results when the forward reaction proceeds at the same rate as the Reversible reaction, reverse reaction. The reaction rates of the forward and backward reactions are generally not zero, but they are equal. Thus, there are no net changes in the concentrations of the reactants and products. Such a state is known as dynamic equilibrium. It is the subject of study of ''equilibrium chemistry''. Historical introduction The Concept learning, concept of chemical equilibrium was developed in 1803, after Claude Louis Berthollet, Berthollet found that some chemical reactions are Reversible reaction, reversible. For any reaction mixture to exist at equilibrium, the reaction rate, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxygen Tank
An oxygen tank is an oxygen storage vessel, which is either held under pressure in gas cylinders, referred to in the industry as high pressure oxygen cylinders, or as liquid oxygen in a cryogenic storage tank. Uses Oxygen tanks are used to store gas for: * medical breathing (oxygen therapy) at medical facilities and at home (high pressure cylinder) * breathing at altitude in aviation, either in a decompression emergency, or constantly (as in unpressurized aircraft), usually in high pressure cylinders * oxygen first aid sets, in small portable high pressure cylinders * gas blending, for mixing breathing gases such as nitrox, trimix and heliox * open-circuit scuba sets - mainly used for accelerated decompression in technical diving, in high pressure cylinders * some types of diving rebreather: oxygen rebreathers and fully closed circuit rebreathers, usually in high pressure cylinders * use in climbing, " Bottled oxygen" refers to oxygen in lightweight high pressure cylinde ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Firefighter
A firefighter (or fire fighter or fireman) is a first responder trained in specific emergency response such as firefighting, primarily to control and extinguish fires and respond to emergencies such as hazardous material incidents, medical incidents, and emergencies that require response from the public that threaten life, property and the environment, as well as to rescue persons from confinement or dangerous situations and preserve evidence. Firefighters may also provide ordinance regulations, safety requirements, and administrative public functions for the communities and areas they are subject to jurisdiction to. Male firefighters are sometimes referred to as firemen (and, less commonly, female firefighters as firewomen). The fire department, also known in some countries as the fire brigade or fire service, is one of the three main emergency services. From urban areas to aboard ships, firefighters have become ubiquitous around the world. The skills required for safe oper ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
