Through examples discovered in the part on acids and also bases proton-transfer procedures are broken into two theoretical steps: (1) donation the a proton by one acid, and (2) acceptance of a proton by a base. (Water served as the basic in the mountain example and as the acid in the base instance ). The hypothetical steps room useful due to the fact that they make it straightforward to watch what species is left ~ an mountain donated a proton and also what species is formed when a base embraced a proton. We shall use hypothetical steps or half-equations in this section, yet you need to bear in psychic that free protons never ever actually exist in aqueous solution.

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Suppose we first consider a weak acid, the ammonium ion. When it donates a proton to any type of other species, we have the right to write the half-equation:

< extNH_4^+ ightarrow extH^+ + extNH_3>

The submicroscopic representations listed below show the donation of the proton of ammonium. The removal of this proton results in NH3, which is conveniently seen at the submicroscopic level.


But NH3 is just one of the compounds we recognize as a weak base. In various other words, once it donates a proton, the weak acid NH4+ is transformed into a weak basic NH3. One more example, this time starting with a weak base, is listed by fluoride ion:

< extF^- + extH^+ ightarrow extHF>

The submicroscopic representation over shows exactly how the addition of a proton to fluoride switch a weak basic (F- in green) into a weak acid (HF).


The situation just described for NH4+ and also NH3 or because that F– and also HF uses to every acids and also bases. Whenever an acid donates a proton, the acid transforms into a base, and also whenever a basic accepts a proton, an acid is formed. An acid and also a base which differ only by the visibility or absence of a proton are referred to as a conjugate acid-base pair. Thus NH3 is referred to as the conjugate basic of NH4+, and also NH4+ is the conjugate acid of NH3. Similarly, HF is the conjugate mountain of F–, and also F– the conjugate base of HF.

The usage of conjugate acid-base pairs permits us to do a very an easy statement around relative strengths of acids and bases. The more powerful an acid, the weaker that conjugate base, and, whereas the more powerful a base, the weaker its conjugate acid.

TABLE (PageIndex1):Important Conjugate Acid-Base Pairs.

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altweak acids have strong conjugate bases