Arrhenius concept

Acid-base chemistry was first satisfactorily explained in molecular terms after Ostwald and Arrhenius established the existence of ions in aqueous solution in 1880-1890 (after much controversy and professional difficulties, Arrhenius received the 1903 Nobel Prize in Chemistry for this theory). As defined at that time, Arrhenius adds form 

This explanation works well in aqueous solution, but it is inadequate for non-aqueous solutions and for gas and solid phase reactions in which H and OH may not exist. Definitions by Brpnsted and Lewis are more appropriate for general use. 

Description Date Acid Base Acid Base 

Liebig -1776 Oxide of N, P, S Reacts with acid SO3 NaOH 

Arrhenius 1894 Forms hydronium ion Forms hydroxide ion HCl NaOH 

Br0nsted-Lowry 1923 Hydrogen ion donor Hydrogen ion acceptor HjO- HjO 

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There are certain limitations of the Arrhenius concept of acids and bases. Acids and bases have been described in terms of their aqueous solutions and not in terms of the entities themselves. The theory is thus applicable exclusively to aqueous solutions. An entity such as HC1 is accounted as an acid only when it is dissolved in water if dissolved in... 

Any text on acids and bases would not be deemed complete if mention were not made of the extended definition of acids and bases that is embodied in the Lowry-Bronsted theory. The theory basically proposed a more general definition of acids and bases to overpower the limitations of the theory arising from the Arrhenius concept. 

The first theory of solutions of weak electrolytes was formulated in 1887 by S. Arrhenius (see Section 1.1.4). If the molar conductivity is introduced into the equations following from Arrhenius concepts of weak electrolytes, Eq. (2.4.17) is obtained, known as the Ostwald dilution law this equation... 

The Arrhenius concept was of basic importance because it permitted quantitative treatment of a number of acid-base processes in aqueous solutions, i.e. the behaviour of acids, bases, their salts and mixtures of these substances in aqueous solutions. Nonetheless, when more experimental material was collected, particularly on reaction rates of acid-base catalysed processes, an increasing number of facts was found that was not clearly interpretable on the basis of the Arrhenius theory (e.g. in anhydrous acetone NH3 reacts with acids in the absence of OH- and without the formation of water). It gradually became clear that a more general theory was needed. Such a theory was developed in 1923 by J. N. Br0nsted and, independently, by T. M. Lowry. 

Eyring and Polanyi extended the Arrhenius concept concerning the nature of barriers to chemical reactivity. They considered the concept of a transition state which can be defined as the highest energy species or configuration in a chemical reaction. Transition-state theory now forms the basis of uncatalyzed and catalyzed chemi-... 

Arrhenius concept A concept stating that acids produce hydrogen ions and bases produce hydroxide ions in aqueous solutions. 

However, the drawback with the Arrhenius concept is that it only applies to aqueous solutions,... 

Note that HA and B are not necessarily neutral. They could be ions that are capable of acting as an acid or a base. This is one of the features of the Bronsted-Lowry concept that broadens the definitions of acids and bases over the Arrhenius concept—there are many more substances that can behave as acids or bases. Further, we can write the reaction including the solvent, water in this case, and the associated Ka. 

According to the Arrhenius conception electrolytes dissociate in solutions to a certain degree that depends solely on the concentration at a given temperature. The dissociation is partial at finite concentration but it increases with increasing dilution and it becomes complete at infinite dilution. At a given temperature... 

The first person to recognize the essential nature of acids and bases was Svante Arrhenius. Based on his experiments with electrolytes, Arrhenius postulated that acids produce hydrogen ions in aqueous solution, and bases produce hydroxide ions. At the time of its discovery the Arrhenius concept of acids and bases was a major step forward in quantifying acid—base chemistry, but this concept is limited because it applies only to aqueous solutions and allows for only one kind of base—the hydroxide ion. A more general definition of acids and bases was suggested independently by the Danish chemist Johannes N. Bronsted (1879-1947) and the English chemist Thomas M. Lowry (1874-1936) in 1923. In terms of the Bronsted—Lowry definition, an acid is a proton (H+) donor, and a base is a proton acceptor. For example, when gaseous HCl dissolves in water, each HCl molecule donates a proton to a water molecule, and so HCl qualifies as a Bronsted-Lowry acid. The molecule that accepts the proton—water in this case—is a Bronsted-Lowry base. 

Note that this reaction is not considered an acid-base reaction according to the Arrhenius concept. 

According to the Arrhenius concept, a base is a substance that produces OH-ions in aqueous solution. According to the Bronsted-Lowry definition, a base is a proton acceptor. The bases sodium hydroxide (NaOH) and potassium hydroxide (KOH) fulfill both criteria. They contain OH- ions in the solid lattice and behave as strong electrolytes, dissociating completely when dissolving in water ... 

Aromatic hydrocarbon one of a special class of cyclic unsaturated hydrocarbons, the simplest of which is benzene. (22.3) Arrhenius concept a concept postulating that acids produce hydrogen ions in aqueous solution, whereas bases produce hydroxide ions. (7.1)... 

Subsequently the data were treated by tiie Arrhenius concept, ie, the logarithm of the reactivity ratios was fdotted versus the redprocal temperature as drown in Fig. 8. This plot expresses quantitatively the effect of temperature on the reactimty ratios of isobutylene and 0-pinene. Evidently, in the higher temperature range, from —50 ... 

Arrhenius concept, 534, 535, 536 Bronsted-Lowry concept, 536, 536 537-538, 537f, 558 examples of, 533 533f neutralization reactions of, 548-549, 548f, 549f, 550... 

Arrhenius Concept Arrhenius (1887) defined acid as a substance that will dissociate to yield a hydrogen ion while base in one that will dissociate to yield a hydroxyl ion in aqueous solution. 

Regarding the question, what do you understand by the term acid or base , many students respond with a pH value ( acids have a small pH value ) or with simple, but misconceived phenomena, which are formulated as follows Adds eat away, are dangerous, yellow, red or acidic [4], Other statements describe acid concepts, which have been mainly learned and remembered Approximately 15% of the answers show the Arrhenius concept (acids contain H + ions) approximately 30% show the Broensted concept (acids release protons), whereby it is not certain if students correctly understand the notion of acids as acid particles. 

Acid-Base Concepts. In the lesson, after becoming familiar with many phenomena on acids and bases as substances, the question is raised as to whether the substance-related Arrhenius concept should be taught, or the particle-related Broensted concept - or the genetic development of both concepts in the form of historically oriented lessons (see Fig. 7.2). Tests on electrical conductivity of solutions of strong acids and bases (see E7.7) confirms that acidic solutions contain H + (aq) ions and basic solutions contain OH (aq) ions. After stating the existence of these ions, one can discuss model drawings and emphasize that the (aq) symbol denotes the complete separation of the ions by hydration (see Figs. 7.10 and 7.11). 

Mental models are thus produced of both acid concepts those of Arrhenius and of Broensted. The Arrhenius concept explains some phenomena in the area of acids and bases, for instance, the neutralization of solutions of strong acids and bases. Terms like weak acids or derived concepts like acid constants or buffer already reach the limits of Arrhenius concept. 

If you missed 43, go to The Arrhenius Concept of Acids and Bases, page 394. 

The Arrhenius concept of acids and bases was a tremendous advance in the understanding of these compounds, but is it limited to aqueous solutions, and a lot of chemistry takes place out of water. In 1923 a Danish chemist, Johannes Bronsted (1879-1947), and an English chemist, Thomas Lowry (1874-1936), proposed a more general way to describe acids and bases centered on the ability of a species to donate or accept a proton, IT. It was not limited to aqueous solutions. Here is how they defined acids, bases and neutralization ... 

The Bronsted-Lowry concept describes many more processes as acid-base reactions than does the Arrhenius concept. For example, the ionization of hydrogen chloride gas as it dissolves in water, HC1 (g) — HC1 (aq), can be described as an acid-base process as the proton from HC1 is transferred to water. 

All compounds that are acids and bases in the Arrhenius concept are also acids and bases in the Bronsted-Lowry scheme. Ammonia gas, NH3fgJ, is very soluble in water, quickly engaging in an equilibrium that produces hydroxide ion making the solution basic. In doing so, water acts as a Bronsted-Lowry acid, donating a proton to ammonia, leaving the remainder of the water molecule, the hydroxide ion, behind. 

In the Arrhenius concept of acids and bases, what species are produced by acids and bases in water What is formed from these species in neutralization ... 

When ammonia is dissolved in water, it can accept a proton from water to form the ammonium ion, and hydroxide ion. Ammonia is a base in the Arrhenius concept because it produces hydroxide ion in water, and it is a base in the Bronsted-Lowiy concept because it is a proton acceptor. 

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