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Acids and bases:
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In chemistry, a base is most commonly thought of as a substance that can accept protons. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are Acid-base extraction is a procedure using sequential Liquid-liquid extractions to purify Acids and bases from mixtures based on their chemical properties Acid-base homeostasis is the part of Human homeostasis concerning the proper balance between Acids and bases, in other words the PH. An acidity function is a measure of the Acidity of a medium or solvent system usually expressed in terms of its ability to donate protons to (or accept protons from a For an individual weak acid or weak base component see Buffering agent. pH is the measure of the acidity or alkalinity of a Solution. The proton affinity, E pa of a Anion or of a neutral Atom or Molecule is a measure of its gas-phase basicity. The self-ionization of water (also autoionization of water, and autodissociation of water) is the chemical reaction in which two water molecules react to produce a In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are A mineral acid is an Acid derived by Chemical reaction from inorganic Minerals as opposed to Organic acids These have Hydrogen An organic acid is an Organic compound with Acidic properties A Strong acid is an Acid that Ionizes completely in an Aqueous solution (not in the case of Sulfuric acid as it is diprotic A superacid is an Acid with an Acidity greater than that of 100% Sulfuric acid, which has a Hammett acidity function ( H 0 A weak acid is an Acid that does not completely donate all of its hydrogens when dissolved in water An organic base is an Organic compound which acts as a base. Organic bases are usually but not always proton acceptors In Chemistry, a base is most commonly thought of as an aqueous substance that can accept Protons This refers to the Brønsted-Lowry theory of acids and In Chemistry, a superbase is an extremely strong base. There is no commonly accepted definition for what qualifies as a superbase but most chemists would accept As the name suggests a non-nucleophilic base is an organic base that is a very Strong base but at the same time a poor Nucleophile. In chemistry a weak base is a Chemical base that does not Ionize fully in an Aqueous solution. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive This refers to the Brønsted-Lowry theory of acids and bases. Alternate definitions of bases include electron pair donors (Lewis), as sources of hydroxide anions (Arrhenius) and can be (commonly) thought of as any chemical compound that, when dissolved in water, gives a solution with a pH higher than 7. lone pair is a (valence electron pair without bonding or sharing with other Atoms They are found in the outermost Electron shell of an atom so lone pairs Svante August Arrhenius ( February 19, 1859 &ndash October 2, 1927) was a Swedish Scientist, originally a Physicist pH is the measure of the acidity or alkalinity of a Solution. 0. Examples of simple bases are sodium hydroxide and ammonia. Sodium hydroxide ( Na[[hydroxide OH]]) also known as Lye, caustic soda and (incorrectly according to IUPAC nomenclature Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor

Bases can be thought of as the chemical opposite of acids. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are A reaction between an acid and base is called neutralization. Bases and acids are seen as opposites because the effect of an acid is to increase the hydronium ion (H3O+) concentration in water, whereas bases reduce this concentration. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are In Chemistry, hydronium is the obsolete name for the Cation H 3 O + derived from Protonation of Water In Chemistry, concentration is the measure of how much of a given substance there is mixed with another substance Bases react with acids to produce water and salts (or their solutions). Water is a common Chemical substance that is essential for the survival of all known forms of Life. A salt, in Chemistry, is defined as the product formed from the neutralisation reaction of Acids and bases.

Contents

Definitions

Main article: acid-base reaction theories

A strong base is a base which hydrolyzes completely, raising the pH of the solution towards 14. Hydrolysis is a Chemical reaction during which one or more water molecules are split into hydrogen and hydroxide ions which may go on to participate in further reactions pH is the measure of the acidity or alkalinity of a Solution. Strong bases, like strong acids, attack living tissue and cause serious burns. They react differently to skin than acids do, so while strong acids are corrosive, we say that strong bases are caustic. Superbases are a class of especially basic compounds and non-nucleophilic bases are a special class of strong bases with poor nucleophilicity. In Chemistry, a superbase is an extremely strong base. There is no commonly accepted definition for what qualifies as a superbase but most chemists would accept As the name suggests a non-nucleophilic base is an organic base that is a very Strong base but at the same time a poor Nucleophile. Bases may also be weak bases such as ammonia, which is used for cleaning. In chemistry a weak base is a Chemical base that does not Ionize fully in an Aqueous solution. Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor Arrhenius bases are water-soluble and these solutions always have a pH greater than 7. pH is the measure of the acidity or alkalinity of a Solution. An alkali is a special example of a base, where in an aqueous environment, hydroxide ions (also viewed as OH-) are donated. In Chemistry, an alkali (from Arabic: Al-Qaly القلي القالي) is a basic, ionic salt of an Alkali metal In Chemistry, hydroxide is the most common name for the diatomic Anion OH− consisting of Oxygen and Hydrogen There are other more generalized and advanced definitions of acids and bases.

The notion of a base as a concept in chemistry was first introduced by the French chemist Guillaume François Rouelle in 1754. Guillaume François Rouelle (1703-1770 was a French chemist and Apothecary. He noted that acids which in those days were mostly volatile liquids (like acetic acid) turned into solid salts only when combined with specific substances. Acetic acid, also known as ethanoic acid, is an organic chemical compound, giving Vinegar its sour taste These substances form a concrete base for the salt [1] and hence the name.

Properties

Some general properties of bases include:

Bases and pH

The pH of (impure) water is a measure of its acidity. Taste (or more formally gustation) is a form of direct Chemoreception and is one of the traditional five Senses Taste (or more formally gustation) is a form of direct Chemoreception and is one of the traditional five Senses In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are Sweet is one of the five Basic tastes and is almost universally regarded as a pleasurable experience An aldehyde is an organic compound containing a terminal Carbonyl group. A ketone (pronounced as key tone) is either the Functional group characterized by a Carbonyl group (O=C linked to two other Carbon atoms or Saponification is the Hydrolysis of an Ester under basic conditions to form an Alcohol and the Salt of a Carboxylic acid Litmus is a Water - Soluble mixture of different Dyes Extracted from Lichens, especially Roccella tinctoria. Phenolphthalein is a Chemical compound with the formula C 20 H 14 O 4 (often written as " HIn pH is the measure of the acidity or alkalinity of a Solution. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are In pure water, about one in ten million molecules dissociate into hydronium ions (H3O+) and hydroxide ions (OH−), according to the following equation:

2H2O(l) → H3O+(aq) + OH-(aq)

The concentration, measured in molarity (M or moles per dm³), of the ions is indicated as [H3O+] and [OH−]; their product is the dissociation constant of water with and has the value 10−7 M. In Chemistry, hydronium is the obsolete name for the Cation H 3 O + derived from Protonation of Water In Chemistry, hydroxide is the most common name for the diatomic Anion OH− consisting of Oxygen and Hydrogen In Chemistry, concentration is the measure of how much of a given substance there is mixed with another substance In Chemistry, concentration is the measure of how much of a given substance there is mixed with another substance The mole (symbol mol) is a unit of Amount of substance: it is an SI base unit, and almost the only unit to be used to measure this The pH is defined as −log [H3O+]; thus, pure water has a pH of 7. (These numbers are correct at 23 °C and slightly different at other temperatures. )

A base accepts (removes) hydronium ions (H3O+) from the solution, or donates hydroxide ions (OH-) to the solution. In Chemistry, hydronium is the obsolete name for the Cation H 3 O + derived from Protonation of Water In Chemistry, hydroxide is the most common name for the diatomic Anion OH− consisting of Oxygen and Hydrogen Both actions will lower the concentration of hydronium ions, and thus raise pH. By contrast, an acid donates H3O+ ions to the solution or accepts OH−, thus lowering pH.

For example, if 1 mole of sodium hydroxide (40 g) is dissolved in water to make 1 litre of solution, the concentration of hydroxide ions becomes [OH−] = 1 mol/L. Sodium hydroxide ( Na[[hydroxide OH]]) also known as Lye, caustic soda and (incorrectly according to IUPAC nomenclature G is the seventh letter in the Latin alphabet. Its name in English is spelled gee or occasionally ge (dʒiː Therefore [H+] = 10−14 mol/L, and pH = −log 10−14 = 14. Note that in this calculation, it is assumed that the activity is equivalent to the concentration, which is not realistic at concentrations over 0. Activity in Chemistry is a measure of an “effective concentration” of a species 1 mol dm-3.

The base dissociation constant or Kb is a measure of basicity. pKb is the negative log of Kb and related to the pKa by the simple relationship pKa + pKb = 14.

Alkalinity is a measure of the ability of a solution to neutralize acids to the equivalence points of carbonates or bicarbonates. Alkalinity or AT is a measure of the ability of a solution to neutralize acids to the Equivalence point of carbonate or bicarbonate

Common Bases

Neutralization of acids

When dissolved in water, the strong base sodium hydroxide decomposes into hydroxide and sodium ions:

NaOH → Na+ + OH-

and similarly, in water hydrogen chloride forms hydronium and chloride ions:

HCl + H2O → H3O+ + Cl-

When the two solutions are mixed, the H3O+ and OH− ions combine to form water molecules:

H3O+ + OH- → 2 H2O

If equal quantities of NaOH and HCl are dissolved, the base and the acid exactly neutralize, leaving only NaCl, effectively table salt, in solution. Sodium bicarbonate or sodium hydrogen carbonate is the Chemical compound with the formula NaHCO3 Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor Sodium hydroxide ( Na[[hydroxide OH]]) also known as Lye, caustic soda and (incorrectly according to IUPAC nomenclature Salt is a Dietary mineral composed primarily of Sodium chloride that is essential for Animal life but toxic to most land plants

Weak bases, such as soda or egg white, should be used to neutralize any acid spills. Neutralizing acid spills with strong bases, such as sodium hydroxide or potassium hydroxide can cause a violent exothermic reaction, and the base itself can cause just as much damage as the original acid spill. Sodium hydroxide ( Na[[hydroxide OH]]) also known as Lye, caustic soda and (incorrectly according to IUPAC nomenclature Potassium hydroxide is the Inorganic compound with the formula K[[hydroxide OH]]

Alkalinity of non-hydroxides

Bases are generally compounds that can neutralize an amount of acids. Both sodium carbonate and ammonia are bases, although neither of these substances contains OH− groups. Sodium carbonate (also known as washing soda or soda ash), is a Sodium Salt of Carbonic acid. Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor Both compounds accept H+ when dissolved in water:

Na2CO3 + H2O → 2 Na+ + HCO3- + OH-
NH3 + H2O → NH4+ + OH-

From this, a pH, or acidity, can be calculated for aqueous solutions of bases. pH is the measure of the acidity or alkalinity of a Solution. Bases also directly act as electron-pair donors themselves:

CO32- + H+ → HCO3-
NH3 + H+ → NH4+

Carbon can act as a base as well as nitrogen and oxygen. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the This occurs typically in compounds such as butyl lithium, alkoxides, and metal amides such as sodium amide. n -Butyllithium (abbreviated BuLi is the most prominent Organolithium reagent. An alkoxide is the Conjugate base of an Alcohol and therefore consists of an organic group bonded to a negatively charged Oxygen atom In Chemistry, an amide is one of three kinds of Compounds (sometimes called acid amide the organic Functional group characterized Sodium amide, commonly called sodamide is the Chemical compound with the formula NaNH2 Bases of carbon, nitrogen and oxygen without resonance stabilization are usually very strong, or superbases, which cannot exist in a water solution due to the acidity of water. In Chemistry, a superbase is an extremely strong base. There is no commonly accepted definition for what qualifies as a superbase but most chemists would accept Resonance stabilization, however, enables weaker bases such as carboxylates; for example, sodium acetate is a weak base. Sodium acetate, (also sodium ethanoate) is the Sodium salt of Acetic acid. In chemistry a weak base is a Chemical base that does not Ionize fully in an Aqueous solution.

Strong bases

A strong base is a basic chemical compound that is able to deprotonate very weak acids in an acid-base reaction. Compounds with a pKa of more than about 13 are called strong bases. Common examples of strong bases are the hydroxides of alkali metals and alkaline earth metals like NaOH and Ca(OH)2. Very strong bases are even able to deprotonate very weakly acidic C-H groups in the absence of water. Hydroxide compounds in order of strongest to weakest:

The cations of these strong bases appear in the 1st and 2nd groups of the periodic table (alkali and earth alkali metals). Potassium hydroxide is the Inorganic compound with the formula K[[hydroxide OH]] Barium hydroxide is the Chemical compound with the formula Ba(OH2 Caesium hydroxide (CsOH is a Chemical compound consisting of an atom of Caesium and a Hydroxide group (also known as Hydroxyl) Sodium hydroxide ( Na[[hydroxide OH]]) also known as Lye, caustic soda and (incorrectly according to IUPAC nomenclature Strontium hydroxide, Sr(OH2 is a caustic Alkali composed of one Strontium Ion and two Hydroxide ions Calcium hydroxide, traditionally called slaked lime, hydrated lime, or pickling lime, is a Chemical compound with the chemical formula Lithium hydroxide (LiOH is a corrosive Alkali hydroxide. It is a white Hygroscopic Crystalline material Rubidium Hydroxide (RbOH is a strong basic chemical and Alkali that is formed by one Rubidium ion and one Hydroxide ion

Group 1 salts of carbanions, amides, and hydrides tend to be even stronger bases due the conjugate acids, which are stable hydrocarbons, amines, and water. Usually these bases are created by adding pure alkali metals such as sodium into the conjugate acid. They are called superbases and it is not possible to keep them in water solution, due to the fact they are stronger bases than the hydroxide ion and as such it will deprotonate the conjugate acid water. In Chemistry, a superbase is an extremely strong base. There is no commonly accepted definition for what qualifies as a superbase but most chemists would accept For example the ethoxide ion (conjugate base of ethanol) in the presence of water will undergo this reaction.

CH3CH2O- + H2O --> CH3CH2OH + OH-


Bases as heterogeneous catalysts

Basic substances can be used as insoluble heterogeneous catalysts for chemical reactions. n -Butyllithium (abbreviated BuLi is the most prominent Organolithium reagent. Lithium diisopropylamide is the Chemical compound with the formula 2NLi Sodium amide, commonly called sodamide is the Chemical compound with the formula NaNH2 Sodium hydride is the Chemical compound with the formula NaH It is primarily used as a strong base in Organic synthesis. Solubility is the characteristic Physical property referring to the ability of a given substance the Solute, to dissolve in a Solvent. Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst A chemical reaction is a process that always results in the interconversion of Chemical substances The substance or substances initially involved in a chemical reaction are called Examples are metal oxides such as magnesium oxide, calcium oxide, and barium oxide as well as potassium fluoride on alumina and some zeolites. Magnesium oxide, or magnesia, is a white solid Mineral that occurs naturally as Periclase and is a source Calcium oxide ( CaO) commonly known as burnt lime, lime or quicklime, is a widely used Chemical compound. Barium oxide, BaO is a white Hygroscopic compound formed by the burning of Barium in Oxygen, although it is often formed through the decomposition Potassium fluoride is the Chemical compound with the formula KF Zeolites (Greek zein, "to boil" lithos, "a stone" are hydrated Aluminosilicate Minerals and have a micro-porous structure A great deal of transition metals make good catalysts, many of which form basic substances. In Chemistry, the term transition metal (sometimes also called a transition element) has two possible meanings It commonly refers to any element in Basic catalysts have been used for hydrogenations, the migration of double bonds, in the Meerwein-Ponndorf-Verley reduction, the Michael reaction, and many other reactions. Hydrogenation is the Chemical reaction that results in addition of Hydrogen (H2 The Meerwein-Ponndorf-Verley Reduction in Organic chemistry is the reduction of Ketones to secondary Alcohols with aluminumisopropylate catalysis The Michael reaction or Michael addition is the Nucleophilic addition of a Carbanion to an alpha beta unsaturated carbonyl compound.

See also

External links

References

  1. ^ The Origin of the Term Base William B. In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are Jensen Journal of Chemical Education • 1130 Vol. 83 No. 8 August 2006
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