Through examples discovered in the part on acids and also bases proton-transfer processes are broken into two theoretical steps: (1) donation the a proton by one acid, and (2) acceptance of a proton by a base. (Water offered as the base in the mountain example and as the acid in the base instance ). The theoretical steps are useful since they do it easy to watch what species is left after ~ an mountain donated a proton and also what varieties is developed when a base embraced a proton. Us shall use theoretical steps or half-equations in this section, yet you have to bear in mind that totally free protons never ever actually exist in aqueous solution.

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

\< \textNH_4^+ \rightarrow \textH^+ +\textNH_3\>

The submicroscopic representations below show the donation of the proton that ammonium. The removal of this proton results in NH3, i beg your pardon is quickly seen at the submicroscopic level.


But NH3 is among the link we recognize as a weak base. In various other words, as soon as 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 noted by fluoride ion:

\<\textF^- + \textH^+ \rightarrow \textHF\>

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


The case just explained for NH4+ and also NH3 or for F– and also HF uses to all acids and bases. At any time an acid donates a proton, the acid transforms into a base, and whenever a basic accepts a proton, an acid is formed. One acid and also a basic which differ only by the presence or lack of a proton are referred to as a conjugate acid-base pair. Hence NH3 is dubbed the conjugate basic of NH4+, and NH4+ is the conjugate acid of NH3. Similarly, HF is the conjugate mountain of F–, and F– the conjugate base of HF.

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

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

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