Terms
Acid
-
A substance that has the potential to donate a proton or accept an electron
pair.
Acidic
-
Having a pH less than 7 or a pOH greater than 7.
Amphiprotic
-
A species that can either donate or accept a proton, e. g. water.
Amphoteric
-
A species that can either donate or accept a hydroxide ion, such as
Al(OH)3. Many
chemistry texts incorrectly use this term to mean that a substance can act
as either an acid or a base.
Arrhenius Model
-
Arrhenius proposed that acids are substances that produce protons
(H+) in
aqueous solution, whereas bases produce hydroxide ions (OH-)
in aqueous
solution. Compare his model with the Bronsted-Lowry definition and the
Lewis
definition.
Base
-
A substance that can accept a proton, release OH-, or donate an
electron pair.
Basic
-
Having a pH greater than 7 or a pOH less than 7.
Bronsted-Lowry Definition
-
Bronsted and Lowry define an acid as a proton (H+) donor and a
base as a proton
acceptor. Compare this model with the Arrhenius Model and the Lewis
definition.
Conjugate Acid
-
A molecule that can be described as a base that has gained one proton.
Conjugate Base
-
A molecule that can be described as an acid that has lost one proton.
Dissociate
-
Separate into its ion constituents.
Lewis Definition
-
Lewis defined an acid as an electron pair acceptor and a base as an
electron pair donor. Compare
his model with the Arrhenius model and the Bronsted-Lowry definition.
Oxyacid
-
A molecule of the form AOn(OH)m, where A is a
non-metal.
Pauling-Ricci rule
-
For oxyacids, the more electron withdrawing (more
electropositive) the non-
metal center, the stronger the acid due to a weakening of the O-H bond. This
trend is approximated by the equation:
PKa = 8 - 9f + 4n, where f is the formal charge on A
when all oxygens are singly bound
to A, and n
represents the number of O atoms bound to A that are not bound to an H.
pH
-
A measure of the hydrogen ion concentration, it is equal to - log
[H+], where [H+] is the concentration of protons.
pKa
-
A measure of the strength of an acid, it is equal to – log
Ka, where Ka is the acid dissociation
constant
in water.
pKb
-
A measure of the strength of a base, it is equal to – log
Kb, where Kb is the base dissociation
constant
in water.
pOH
-
A measure of the hydroxide ion concentration, it is equal to - log
[OH-], where [OH-] is the concentration of hydroxide ions.
Strong Acid
-
An acid with a pKa less than zero. Strong acids
completely dissociate in water.
Strong Base
-
A base with a pKb less than zero. Strong bases
completely
dissociate in water.
Weak Acid
-
An acid with a pKa greater than zero. Weak acids do
not completely dissociate in water.
Weak Base
-
A base with a pKb greater than zero. Weak bases do not
completely dissociate in
water.
