Bronsted-Lowery theory

The two clear, colorless gases mix, and a white solid of ammonium chloride forms. I show the intermediate formation of the ions in the equation so that you can better see what s actually happening. The HCl transfers an H to the ammonia. That s basically the same thing that happens in the HCl/NaOH reaction, but the reaction involving the ammonia can t be classified as an acid-base reaction, because it doesn t occur in water, and it doesn t involve the hydroxide ion. But again, the same basic process is taking place in both cases. In order to account for these similarities, a new acid-base theory was developed, the Bronsted-Lowery theory. 

The Bronsted-Lowery theory attempts to overcome the limitations of the Arrhenius theory by defining an acid as a proton (H ) donor and a base as a proton (Tl ) acceptor. The base accepts the H by furnishing a lone pair of electrons for a coordinate-covalent bond, which is a covalent bond (shared pair of electrons) in which one atom furnishes both of the electrons for the bond. Normally, one atom furnishes one electron for the bond and the other atom furnishes the second electron (see Chapter 7). In the coordinate-covalent bond, one atom furnishes both bonding electrons. 

I discuss acid-base reactions under the Bronsted-Lowery theory in the section Give me that proton Bronsted-Lowery acid-base reactions, later in this chapter. 

With the Arrhenius theory, acid-base reactions are neutralization reactions. With the Bronsted-Lowery theory, acid-base reactions are a competition for a proton. For example, take a look at the reaction of ammonia with water ... 

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