Bronsted-Lowry base A proton acceptor

A base is a substance that can accept a proton. (Some chemists describe Bronsted-Lowry bases as proton-acceptors. )... 

Every base that we have discussed thus far—whether OH, H2O, an amine, or an anion—is an electron-pair donor. Everything that is a base in the Bronsted-Lowry sense (a proton acceptor) is also a base in the Lewis sense (an electron-pair donor). In the Lewis theory, however, a base can donate its electron pair to something other than H". ... 

Every base that we have discussed thus far—whether OH , H2O, an amine, or an anion—is an electron-pair donor. Everything that is a base in the Bronsted-Lowry sense (a proton acceptor) is also a base in the Lewis sense (an electron-pair donor). In the Lewis theory, however, a base can donate its electron pair to something other than H. The Lewis definition therefore greatly increases the number of species that can be considered acids in other words, is a Lewis acid but not the only one. For example, the reaction between NH3 and BF3 occurs because BF3 has a vacant orbital in its valence shell, ooo (Section 8.7) It therefore acts as an electron-pair acceptor (a Lewis acid) toward NH3, which donates the electron pair ... 

Bronsted-Lowry bases are proton acceptors and must have an available electron pair (either a lone pair or a jr bond). 

To see what s going on in an acid-base reaction, keep your eye on the proton. For example, when a Bronsted-Lowry acid HA is placed in water, it reacts reversibly with water in an acid-dissociation equilibrium. The acid transfers a proton to the solvent, which acts as a base (a proton acceptor). The products are the hydronium ion, H30+ (the conjugate acid of H20), and A- (the conjugate base of HA) ... 

Bronsted-Lowry base A species that acts as a proton acceptor. 

In the Bronsted-Lowry concept, an acid is a proton donor, a base a proton acceptor and neutralization is the donation of one proton by an acid to a base. 

Bronsted-Lowry base A substance (molecule or ion) that acts as a proton acceptor. (Section 16.2) buffer capacity The amoimt of add or base a buffer can neutralize before the pH begins to change appredably. (Section 17.2)... 

The transfer of a proton always involves both an acid (donor) and a base (acceptor). In other words, a substance can function as an acid only if another substance simultaneously behaves as a base. To be a Bronsted-Lowry acid, a molecule or ion must have a hydrogen atom it can lose as an H ion. To be a Bronsted-Lowry base, a molecule or ion must have a nonbonding pair of electrons it can use to bind the H ion. 

A useful definition of acids and bases is that independently introduced by Johannes Bronsted (1879-1947) and Thomas Lowry (1874-1936) in 1923. In the Bronsted-Lowry definition, acids are proton donors, and bases are proton acceptors. Note that these definitions are interrelated. Defining a base as a proton acceptor means an acid must be available to provide the proton. For example, in reaction 6.7 acetic acid, CH3COOH, donates a proton to ammonia, NH3, which serves as the base. 

J. N. Bronsted and T. M. Lowry independently arrived at definitions of an acid and a base that do not involve water. They recognized that the essential characteristic of an acid-base reaction was the transfer of a hydrogen ion (proton) from one species (the acid) to another (the base). According to these definitions, an acid is a proton donor and a base is a proton acceptor. The proton must be donated to some other species so there is no acid without a base. According to Arrhenius, HC1 is an acid because... 

The concepts of the Lowry-Bronsted theory may explain the various reactions that take place during many non-aqueous titrations. Thus, an acid is a proton donor and a base is a proton acceptor. Therefore, when an acid HA undergoes dissociation it gives rise to a proton and the conjugate base A of the acid ... 

In 1923, Bronsted and Lowry defined an acid as a proton donor and a base as a proton acceptor. 

Water can provide both H and OH H O H"+OH- According to Bronsted-Lowry theory, a water molecule can accept a proton, thereby becoming a hydronium ion. In this case, water is acting as a base (proton acceptor). H2O + H" H3O" 1 point given for correct Bronsted-Lowry concept of water being able to accept a proton resulting in a hydronium ion. 

Under the Bronsted-Lowry definition, an acid is a substance that donates a hydrogen ion (H+) in an acid-base reaction, while a base is a substance that accepts that hydrogen ion from the acid. When ionized to form a hydrogen cation, hydrogen loses its one and only electron and is left with only a single proton. For this reason, Bronsted-Lowry acids are often called proton donors, and Bronsted-Lowry bases are called proton acceptors. 

Drugs cross biological membranes most readily in the unionised state. The unionised drug is 1000-10000 times more lipid-soluble than the ionised form and thus is able to penetrate the cell membrane more easily. Chemical compounds in solution are acids, bases or neutral. The Bronsted-Lowry definition of an acid is a species that donates protons (H+ ions) while bases are proton acceptors. Strong acids and bases in solution dissociate almost completely into their conjugate base and H+. Weak acids and weak bases do not completely dissociate in solution, and exist in both ionised and unionised states. Most drugs are either weak acids or weak bases. For an acid, dissociation in solution is represented by ... 

The Arrhenius theory accounts for the properties of many common acids and bases, but it has important limitations. For one thing, the Arrhenius theory is restricted to aqueous solutions for another, it doesn t account for the basicity of substances like ammonia (NH3) that don t contain OH groups. In 1923, a more general theory of acids and bases was proposed independently by the Danish chemist Johannes Bronsted and the English chemist Thomas Lowry. According to the Bronsted-Lowry theory, an acid is any substance (molecule or ion) that can transfer a proton (H + ion) to another substance, and a base is any substance that can accept a proton. In short, acids are proton donors, bases are proton acceptors, and acid-base reactions are proton-transfer reactions ... 

When a Bronsted-Lowry base such as NH3 dissolves in water, it accepts a proton from the solvent, which acts as an acid. The products are the hydroxide ion, OH (the conjugate base of water), and the ammonium ion, NH4+ (the conjugate acid of NH3). In the reverse reaction, NH4+ acts as the proton donor, and OH-acts as the proton acceptor ... 

Since all proton acceptors have an unshared pair of electrons, and since all electron-pair donors can accept a proton, the Lewis and the Bronsted-Lowry definitions of a base are simply different ways of looking at the same property. All Lewis bases are Bronsted-Lowry bases, and all Bronsted-Lowry bases are Lewis bases. The Lewis definition of an acid, however, is considerably more general than the Bronsted-Lowry definition. Lewis acids include not only H+ but also other cations and neutral molecules having vacant valence orbitals that can accept a share in a pair of electrons donated by a Lewis base. 

According to the Arrhenius theory, acids (HA) are substances that dissociate in water to produce H + (aq). Bases (MOH) are substances that dissociate to yield OH aq). The more general Bransted-Lowry theory defines an acid as a proton donor, a base as a proton acceptor, and an acid-base reaction as a proton-transfer reaction. Examples of Bronsted-Lowry acids are HC1, NH4+, and HSO4- examples of Bronsted-Lowry bases are OH-, F-, and NH3. 

There are several definitions of acids and bases. According to the Bronsted-Lowrv definition, an acid is a proton donor and a base is a proton acceptor. Any compound that has a hydrogen can potentially act as a Bronsted-Lowry acid (although the strength of the acid can vary enormously). Therefore, H—A is used as a general representation for an acid. To accept a proton, most bases... 

According to the Lewis definition, an acid is an electron pair acceptor and a base is an electron pair donor. All Bronsted-Lowry bases are also Lewis bases. However, Lewis acids include many species that are not proton acids instead of H+, they have some other electron-deficient species that acts as the electron pair acceptor. An example of a Lewis acid-base reaction is provided by the following equation. In this reaction the boron of BF3 is electron/deficient (it has only six electrons in its valence shell). The oxygen of the ether is a Lewis base and uses a pair of electrons to form a bond to the boron, thus completing boron s octet. 

Bronsted-Lowry base (Section 4.1) A proton acceptor. 

One very important thing to remember is that an acid and base are always present in these reactions. In order for a molecule or ion to donate a proton, there has to be another ion or molecule to receive it. In addition, in reversible acid-base reactions, the roles of the substances as proton donor or acceptor will switch in the reverse reaction. In the example below, note how water (a Bronsted-Lowry base in this reaction) accepts a proton to form a hydronium ion in the forward reaction. In the reverse reaction, the hydronium ion (Bronsted-Lowry acid) donates a proton and, after losing the proton, becomes the water molecule once again ... 

The correct answer is (C). HzO accepts a proton from HC2H302. Proton acceptors are Bronsted-Lowry bases. Water can act as a Bronsted-Lowry acid or base, but in this reaction it is a base. 

In many chemistry references, Bronsted-Lowry acids are called "proton donors." Bronsted-Lowry bases are called "proton acceptors." Although these terms are common, they create a false impression about the energy that is involved in acid-base reactions. Breaking bonds always requires energy. For example, removing a proton from a hydrochloric acid molecule requires 1.4 x 103 kJ/mol. This is far more energy than the word donor" implies. 

A Bronsted-Lowry acid is any substance that is capable of donating a proton, whereas a Bronsted-Lowry base is any substance that is capable of accepting a proton. The loss of a proton by an acid gives rise to an entity that is a potential proton acceptor and thus a base it is called the conjugate base of the parent acid. Examples of acids reacting with bases are given in Table 1.16. The reactions listed in Table 1.16 are spontaneous in the direction that favors production of the weaker acid and base. Compounds that may act as bases and acids are referred to as amphoteric. 

T, F A conjugate base is formed from an acid that loses a proton. Bronsted-Lowry acids are proton donors and not acceptors. 

NHj contains no hydroxide ions yet when you put it in water it increases the hydroxide ion concentration. To account for examples such as this we have what is known as the Bronsted-Lowry (Johannes Bronsted and Thomas Lowry) theory of acids and bases. In this definition an acid is any substance that donates protons in a reaction and a base is any substance that accepts protons in a reaction. This is basically (no pun intended) the same as the Arrhenius definition of acids because if a substance readily donates protons in a reaction it will also increase the hydronium ion concentration when placed in water. The definition of a base, though, is expanded to include any substance that readily accepts protons in a reaction, and that substance doesn t have to contain hydroxide ions. Let s continue with our above example. There, NH contributed to the Off concentration when dissolved in water. But NH3 is also a proton acceptor (which we have defined as a base) because it picks up a proton to become as in... 

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. 

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 ... 

Bronsted-Lowry definition (model) a model proposing that an acid is a proton donor, and a base is a proton acceptor. (7.1)... 

The nucleophile, the ammonia molecule, is also acting as a base, while the electrophile, the proton, is also acting as an acid. So a base may also be thought of as a nucleophile, because both are electron rich species and seek positive centres. The above reaction between the ammonia and the proton may be classified as a Bronsted-Lowry acid/base reaction. It may also be classed as a Lewis acid/base reaction, depending on whether one views the ammonia as a proton acceptor or as a donor of a lone pair of electrons. 

Base Usually either a proton acceptor (Bronsted-Lowry definition) or an electron pair donor (Lewis definition), but there are other definitions. 

C is correct. The leveling effect in water occurs because water readily accepts all protons from both acids. The equilibrium in water is so far to the right for both reactions that no comparison can be made. Although acetic acid accepts protons from both HC1 and HC104, it does not do so as readily as water (it is a weaker proton acceptor or Bronsted-Lowry base). Thus, an equilibrium is established for both reactions, and the equilibriums can be compared. 

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