Gases Bronsted-Lowry

At the microscopic level, acids are defined as proton (H ) donors (Bronsted-Lowry theory) or electron-pair acceptors (Lewis theory). Bases are defined as proton (H+) acceptors (Bronsted-Lowry theory) or electron-pair donors (Lewis theory). Consider the gas-phase reaction between hydrogen chloride and ammonia ... 

The Bronsted-Lowry definition is not limited to aqueous solutions it can be extended to reactions in the gas phase. For example, consider the reaction between gaseous hydrogen chloride and ammonia that we discussed when we studied diffusion (Chapter 5) ... 

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. 

Boyle s law The gas law stating that, at constant temperature and amount of gas, the volume occupied by a gas is inversely proportional to the applied (external) pressure V - IP. (144) Bronsted-Lowry acid-base definition A model of acid-base behavior based on proton transfer, in which an acid and a base are defined, respectively, as species that donate and accept a proton. (587) buffer (See acid-base buffer.)... 

The real value of the Lewis model for acids and bases is that it covers many reactions that do not involve Bronsted-Lowry acids. For example, consider the gas-phase reaction between boron trifluoride and ammonia ... 

Boyle s law the volume of a given sample of gas at constant temperature varies inversely with the pressure. (5.2) Breeder reactor a nuclear reactor in which fissionable fuel is produced while the reactor runs. (20.6) Bronsted-Lowry definition (model) a model proposing that an acid is a proton donoi and a hase is a proton acceptor (7.1)... 

Because the emphasis in the Bronsted-Lowry concept is on proton transfer, the concept also applies to reactions that do not occur in aqueous solution. In the reaction between gas phase HCl and NH3, for example, a proton is trcuisferred from the acid HCl to the base NH3 ... 

Bronsted-Lowry acid Bronsted-Lowry base flue gas scrubbers... 

Bronsted-Lowry Acid-Base Reactions Hydrogen chloride gas escapes from a hydrochloric acid solution and combines with ammonia gas that has escaped from an aqueous ammonia solution. The resulting cloud is solid ammonium chloride that is dispersed in air. 

Lewis proposed his stiU broader and more useful definition of acids and bases in the late 1920s and early 1930s. Classifying acids as electron-pair acceptors and bases as electron-pair donors, he thereby liberated acid—base theory entirely from its former dependence on the presence of hydrogen. The advantage of the Lewis definition is that a larger number of reactions can be classified as acid-base than under either the Arrhenius or Bronsted-Lowry definitions. The classic example used to demonstrate the more general nature of the Lewis definition is the gas-phase reaction between boron trifluoride and ammonia, as represented in Equation (4.1) ... 

An acid was once defined simply as a substance which produces hydrogen ions, or protons. However, the simple proton, H , is never found under ordinary conditions, and this definition required amendment. Bronsted and, independently, Lowry, therefore redefined an acid as a susbstance able to donate protons to other molecules or ions, and a base as a substance capable of accepting such protons. If we consider hydrogen chloride, HCl, as an example, the HCl molecule is essentially covalent, and hydrogen chloride (gas or liquid) contains no protons. But anhydrous hydrogen chloride in benzene will react with anhydrous ammonia ... 

Nucleophilicity. A distinction is usually made between nucleophilicity and Lowry-Bronsted basicity [213]. The latter involves specifically reaction at a proton which is complexed to a Lewis base (usually H2O), while the former refers to reactivity at centers other than H. Linear correlations have been shown for gas-phase basicity (proton affinity) and nucleophilicity of nitrogen bases toward CH3I in solution [214] where the solvent is not strongly involved in charge dispersal. In each case, reaction of the base/nucleophile... 

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