Conjugate (acid-base theory)

A conjugate acid, within the <a href="/facts/Br%C3%B8nsted%E2%80%93Lowry_acid%E2%80%93base_theory/bqxQnJoX">Brønsted–Lowry acid–base theory</a>, is a <a href="/facts/Chemical_compound/37FXqqtv">chemical compound</a> formed when an acid <a href="/facts/Protonation/q5Gf9z0M">gives a proton</a> (<a href="/facts/Hydron_(chemistry)/v5Qkumvm">H+</a>) to a <a href="/facts/Base_(chemistry)/M9wA7qeM">base</a>—in other words, it is a base with a <a href="/facts/Hydrogen_ion/6UbSyoz4">hydrogen ion</a> added to it, as it loses a hydrogen ion in the reverse reaction. On the other hand, a conjugate base is what remains after an acid has donated a proton during a chemical reaction. Hence, a conjugate base is a substance formed by the <a href="/facts/Deprotonation/SmUSh369">removal of a proton</a> from an acid, as it can gain a hydrogen ion in the reverse reaction. Because <a href="/facts/Polyprotic_acid/FySU18n1">some acids</a> can give multiple protons, the conjugate base of an acid may itself be acidic.
In summary, this can be represented as the following <a href="/facts/Chemical_reaction/GpqWlKrz">chemical reaction</a>:

acid
 
 +
 
 base
 
 
 
 
 
 
 
 
 
 ↽
 
 
 
 
 −
 
 
 
 
 
 
 
 
 −
 
 
 
 
 ⇀
 
 
 
 
 
 
 
 
 
 conjugate base
 
 +
 
 conjugate acid
 
 
 
 {\displaystyle {\text{acid}}+{\text{base}}\;{\ce {<=>}}\;{\text{conjugate base}}+{\text{conjugate acid}}}

<a href="/facts/Johannes_Nicolaus_Br%C3%B8nsted/pw6sL4oc">Johannes Nicolaus Brønsted</a> and <a href="/facts/Martin_Lowry/XxL9Ftxo">Martin Lowry</a> introduced the Brønsted–Lowry theory, which said that any compound that can give a proton to another compound is an acid, and the compound that receives the proton is a base. A proton is a subatomic particle in the nucleus with a unit positive electrical charge. It is represented by the symbol H+ because it has the <a href="/facts/Atomic_nucleus/orpIm5Xl">nucleus</a> of a hydrogen <a href="/facts/Atom/FoQ4kGN5">atom</a>, that is, a <a href="/facts/Hydron_(chemistry)/v5Qkumvm">hydrogen cation</a>.
A <a href="/facts/Cation/wrbwhF3z">cation</a> can be a conjugate acid, and an <a href="/facts/Anion/wrbwhF3z">anion</a> can be a conjugate base, depending on which <a href="/facts/Chemical_substance/EWcXU41d">substance</a> is involved and which <a href="/facts/Acid%E2%80%93base_reaction/z8pbL0X8">acid–base theory</a> is used. The simplest anion which can be a conjugate base is the <a href="/facts/Solvated_electron/mLplrtI8">free electron in a solution</a> whose conjugate acid is the atomic hydrogen.

Conjugate (acid-base theory) open-in-new

Conjugate (acid-base theory)