Acidity Arrhenius

Arrhenius acid, Bransted-Lowry acid Arrhenius acid, Bransted-Lowry acid Arrhenius base, Bransted-Lowry base Arrhenius acid, Bransted-Lowry acid amphoteric hydroxide (can act as either an acid or base)... 

The term acid is derived from the Latin word acidus meaning sour. Arrhenius (1859-1927) of Sweden introduced the idea of compounds splitting into their constituent ions. Based on this idea, he was able to explain that the concentration of the hydrogen ions in water (aqueous solution) determined the strength of an acid. Arrhenius was awarded the Nobel Prize in 1903 for his work on ionization. Acids are classified as naturally occurring acids and mineral acids. 

Acid (Arrhenius or Bronsted-Lowry) A substance that produces H+(aq) ions in aqueous solution. Strong acids ionize completely or almost completely in dilute aqueous solution weak acids ionize only slightly. 

An understanding of the chemical mechanisms that give rise to the properties of acids evolved from a number of different theories of the nature of acids. Arrhenius proposed the Arrhenius Concept of Bases that an acid is a... 

Fig. 27 Corrosion of Al 99.5 in static nitric acid Arrhenius diagram [32].

Almost 50 years after Liebig s definition of acids Arrhenius presented his theory as his doctoral thesis, entitled "Reserches sur la Conductibilite Galvanique du Electrolytes," before the Swedish Academy of Science on June 6,1883. In this thesis he gave data pertaining to the dissociation of salts and acids in dilute solutions into "electrically charged ions." The thesis was accepted with a passing grade, but the oral defense was rated with a superior performance. 

Acid (Arrhenius definition) a substance that produces hydrogen ions, H, (hydronium ion, H30 ) when it dissolves in water. (4.4 and 16.1) (Brpnsted-Lowry definition) the species (molecule or ion) that donates a proton to another species in a proton-transfer reaction. (4.4 and 16.2)... 

Arrhenius Acids Arrhenius s observations form the basis of a definition of acids. Auhenius acids, such as the nitric acid shown here, produce hydronium ions in aqueous solution. 

TABLE 8.1 The acidity dependence and Arrhenius parameters for the nitration of some cations in... 

Further problems arise if measurements of the rate of nitration have been made at temperatures other than 25 °C under these circumstances two procedures are feasible. The first is discussed in 8.2.2 below. In the second the rate profile for the compound imder investigation is corrected to 25 °C by use of the Arrhenius parameters, and then further corrected for protonation to give the calculated value of logio/i fb. at 25 °C, and thus the calculated rate profile for the free base at 25 °C. The obvious disadvantage is the inaccuracy which arises from the Arrhenius extrapolation, and the fact that, as mentioned above, it is not always known which acidity functions are appropriate. 

Kinetic data are available for the range 7S S 98 i % sulphuric acid, and Arrhenius parameters at several acidities. The relative rate was obtained as before. 

The case of i-methyl-4-quinolone is puzzling. The large proportion of the 3-nitro isomer formed in the nitration (table 10.3 cf. 4-hydroxyquinoline) might be a result of nitration via the free base but this is not substantiated by the acidity dependence of the rate of nitration or by the Arrhenius parameters. From r-methyl-4-quinolone the total yield of nitro-compounds was not high (table ro.3). 

According to the theory proposed by Svante Arrhenius a Swedish chemist and winner of the 1903 Nobel Prize in chemistry an acid is a substance that ionizes to give protons when dissolved m water... 

The acid dissociation constant has the same form m Brpnsted-Lowry as m the Arrhenius approach but is expressed m the concentration of H30" rather than The concentration terms [H30" ] and [H" ] are considered equivalent quantities m equilibrium constant expressions... 

This chapter sets the stage for all of the others by reminding us that the relationship between structure and properties is what chemistry is all about It begins with a review of Lewis structures moves to a discussion of the Arrhenius Brpnsted-Lowry and Lewis pictures of acids and bases and the effects of structure on acidity and basicity... 

According to the Arrhenius definitions an acid ionizes m water to pro duce protons (H" ) and a base produces hydroxide ions (HO ) The strength of an acid is given by its equilibrium constant for ionization m aqueous solution... 

The Br0nsted-Lowry approach to acids and bases is more generally use ful than the Arrhenius approach... 

The Lewis definitions of acids and bases provide for a more general view of acid-base reactions than either the Arrhenius or Br0nsted-Lowry pic ture A Lewis acid is an electron pair acceptor A Lewis base is an electron pair donor The Lewis approach incorporates the Br0nsted-Lowry approach as a subcategory m which the atom that accepts the electron pair m the Lewis acid is a proton... 

Achiral (Section 7 1) Opposite of chiral An achiral object is supenmposable on its mirror image Acid According to the Arrhenius definition (Section 1 12) a substance that ionizes in water to produce protons Accord mg to the Br0nsted-Lowry definition (Section 1 13) a sub stance that donates a proton to some other substance According to the Lewis definition (Section 1 17) an electron pair acceptor... 

This system of nomenclature has withstood the impact of later experimental discoveries and theoretical developments that have since the time of Guyton de Morveau and Lavoisier greatiy altered the character of chemical thought, eg, atomic theory (Dalton, 1802), the hydrogen theory of acids (Davy, 1809), the duahstic theory (Berzehus, 1811), polybasic acids (Liebig, 1834), Periodic Table (Mendeleev and Meyer, 1869), electrolytic dissociation theory (Arrhenius, 1887), and electronic theory and modem knowledge of molecular stmcture. 

Hydrogen was recognized as the essential element in acids by H. Davy after his work on the hydrohalic acids, and theories of acids and bases have played an important role ever since. The electrolytic dissociation theory of S. A. Arrhenius and W. Ostwald in the 1880s, the introduction of the pH scale for hydrogen-ion concentrations by S. P. L. Sprensen in 1909, the theory of acid-base titrations and indicators, and J. N. Brdnsted s fruitful concept of acids and conjugate bases as proton donors and acceptors (1923) are other land marks (see p. 48). The di.scovery of ortho- and para-hydrogen in 1924, closely followed by the discovery of heavy hydrogen (deuterium) and... 

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