chem whatarethemechanismsofchemicalchange
Reactivity 3.1.6 - strong and weak acids and bases differ in the extent of ionisation
- the position of equilibrium for the dissociation of an acid or a base defines its strength
- if the acid or base dissociates fully, its equilibrium lies to the right and is said to be a strong acid or base
- if the acid or base dissociates only partially, its equilibrium lies to the left and is said to be a weak acid or base
dissociation reactions
dissociation of acids
dissociation of a strong acid example
- since
dissociates fully, the reverse reaction can be considered to be negligible, so the reaction is written without the equilibrium sign
dissociation of a weak acid example
- since
dissociates partially, it is written with an equilibrium sign
==acid dissociation reactions favour the production of the weaker conjugate==
dissociation of bases
strong base dissociation example:
- since
dissociates fully, its dissociation is written without equilibrium signs
weak base dissociation example:
- since
is a weak base as it ionises only partially, its equilibrium lies to the left and the concentration of ions is low
base dissociation reactions favour the production of the weaker conjugate
acids and bases to remember
strong:
| acids | bases |
|---|---|
weak:
| acids | bases |
|---|---|
| organic acids | |
| amines | |
the strength of a Brønsted-Lowry acid depends on the ease with which it dissociates - which depends on the strength of the bond.
weaker bonds and longer bonds require less energy to break, so as an example: the acid strength of hydrogen halides increases down the group
distinguishing between strong and weak acids and bases
due to the greater ionisation in solution, strong acid sand bases will contain a higher concentration of ions than weak acids and weak bases. this can then be used to distinguish between them
electrical conductivity
- the electrical conductivity of a solution depends on the concentration of mobile ions
- strong acids and bases will show higher conductivity than weak acids and bases
(given the concentrations of solutions compared are equal)
rate of reaction
the reactions of acids with bases depend on the concentration of
as it is a measure of the concentration of