An acid (... from the Latin acidus meaning sour) is traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion activity greater than in pure water, i.e. a pH less than 7.0 in its standard state. That approximates the modern definition of Johannes Nicolaus Brønsted and Martin Lowry, who independently defined an acid as a compound which donates a hydrogen ion (H) to another compound. Common examples include acetic acid and sulfuric acid.
An acid-base reaction is a chemical reaction that occurs between an acid and a base. Several concepts that provide alternative definitions for the reaction mechanisms involved and their application in solving related problems exist. Despite several differences in definitions, their importance becomes apparent as different methods of analysis when applied to acid-base reactions for gaseous or liquid species, or when acid or base character may be somewhat less apparent.
pH is a measure of the acidity or alkalinity of a solution. It approximates but is not equal to p[H], the negative logarithm (base 10) of the molar concentration of dissolved hydrogen ions (H). Crudely, this matches the number of places behind the decimal point, so for example 0.1 molar hydrochloric acid should be near pH 1 and 0.0001 molar HCl should be near pH 4.
Within the Brønsted-Lowry theory of acids and bases, a conjugate acid is the acid member, HX, of a pair of two compounds that transform into each other by gain or loss of a proton. A conjugate acid can also be seen as the chemical substance that releases, or donates, a proton in the forward chemical reaction, hence, the term acid. The base produced, X, is called the conjugate base, and it absorbs, or gains, a proton in the backward chemical reaction.
A buffer solution is an aqueous solution consisting of a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid. It has the property that the pH of the solution changes very little when a small amount of strong acid or base is added to it. Buffer solutions are used as a means of keeping pH at a nearly constant value in a wide variety of chemical applications. Many life forms thrive only in a relatively small pH range; an example of a buffer solution is blood.
A pH meter is an electronic instrument used to measure the pH of a liquid (though special probes are sometimes used to measure the pH of semi-solid substances). A typical pH meter consists of a special measuring probe connected to an electronic meter that measures and displays the pH reading.
Em Química, anfiprótico refere-se a um solvente ou meio que possa doar ou receber prótons. Podem assim actuar como ácidos ou bases, e portanto são anfotéricas. No entanto, as substâncias anfotéricas não são necessariamente anfipróticas.
A Lewis acid, A, is a chemical substance that can accept a pair of electrons from a Lewis base, B, that acts as an electron-pair donor, forming an adduct, AB as given by the following: A + :B → A—B Gilbert N. Lewis proposed this definition, which is based on chemical bonding theory, in 1923. Brønsted-Lowry acid-base theory was published in the same year.
An oxyanion or oxoanion is a chemical compound with the generic formula AxOy (where A represents a chemical element and O represents an oxygen atom). Oxyanions are formed by a large majority of the chemical elements. The formulae of simple oxyanions are determined by the octet rule. The structures of condensed oxyanions can be rationalized in terms of AOn polyhedral units with sharing of corners or edges between polyhedra.
A predominance diagram purports to show the conditions of concentration and pH where a chemical species has the highest concentration in solutions in which there are multiple acid-base equilibria. The lines on a predominance diagram indicate where adjacent species have the same concentration. Either side of such a line one species or the other predominates, that is, has higher concentration relative to the other species.
See also: Fish as food. For the UK band, see Seafood (band). Seafood is any sea animal or plant that is served as food and eaten by humans. Seafoods include seawater animals, such as fish and shellfish. By extension, in North America although not generally in the United Kingdom, the term seafood is also applied to similar animals from fresh water and all edible aquatic animals are collectively referred to as seafood.
Alexandra Elizabeth "Alex" Kingston (born 11 March 1963) is an English actress. She is most widely known for her role as Dr. Elizabeth Corday on the NBC medical drama ER, and also well known as Professor River Song in Doctor Who.