Acidity of simple acids
The simplest molecular acids are HnX where element X is more electronegative than H.
The tendency of an acid to donate a proton to a base is referred to as its acid strength. The acid strength of HnX can be correlated with the location of X in the periodic table.
Show/Hide Electronegativity
As shown in the table, the acidity of HnX is higher for X farther to the right across a row and farther down a group the periodic table.
Strong acids react with water to the extent (extent of conversion of reactants to products - often expressed as a percentage) of 100%.
Weak acids react with water to the extent (extent of conversion of reactants to products - often expressed as a percentage) of less than 5%.
The tendency of an acid to donate a proton to a base is referred to as its acid strength. The acid strength of HnX can be correlated with the location of X in the periodic table.
Show/Hide Electronegativity
Electronegativity is the tendency of a bonded atom to attract electrons to itself. In the bond H-X where X has a higher electronegativity than H, there is unequal sharing of the bonding electrons, and the H is slightly positive and the X is slightly negative.
increasing acidity  | |||||
| CH4 | NH3 | H2O | HF |  | |
| H2S | HCl | ||||
| weak acids | HBr | ||||
| strong acids | HI | ||||
Strong acids react with water to the extent (extent of conversion of reactants to products - often expressed as a percentage) of 100%.
H3O+ and A– are major species (A major species is present in relatively high concentration (>10% of the concentration of other species)) in an aqueous solution of a strong acid.
HA is a minor species (A minor species is present in very low concentration - less than 10% of the concentration of major species) in an aqueous solution of a strong acid.
HA is a minor species (A minor species is present in very low concentration - less than 10% of the concentration of major species) in an aqueous solution of a strong acid.
Weak acids react with water to the extent (extent of conversion of reactants to products - often expressed as a percentage) of less than 5%.
The equilibrium arrow (
) indicates that the reverse reaction is more important than the forward reaction.
HA is a major species and H3O+ and A– are minor species (A minor species is present in very low concentration - less than 10% of the concentration of major species) in an aqueous solution of a weak acid.
) indicates that the reverse reaction is more important than the forward reaction.HA is a major species and H3O+ and A– are minor species (A minor species is present in very low concentration - less than 10% of the concentration of major species) in an aqueous solution of a weak acid.