Summary A* student notes CIE A-level Chemistry - Unit 25 - Equalibria

Equilibria Assumptions for ka
-




-



He provided by water is
negligable
-

The CHA] is the
Same as at the start as so lit
dissociate
Acids and Bases
Conjugate the value of ka indicates the level of dissociation
-




-




High value
-


molecules separated by the transfer of a
proton
-


equalibrium lies to the
right
stronger acid
-




e .




g CHzCOOH +
H2O CH300 + HzOt -
low value

acid
-
base
acid rbase -
equalibrium lies to the left
weak acid
-




Bronsted base pK:
-


A species that can act as a
proton acceptor used to compare strength of weak acids


Bronsted acid pka -log (ka)
=




A species that can act as donor
a
proton
-




kn-ionic product of water
In this example CHzCOOH CH 00 + and H20HyOt -
water exists is an equilibrium
,
acid-base pairs
are
conjugate H20H
+
+ Ot



PH -

kw is the equilibrium constant for the dissociation o
-

indicates the acidity and basicity of a solution water



[H ] [OH]
-log [H )
kw
+


pH
+
= =




# )
+
is the concentration of
t
in the solution small amounts of water dissociate so its
-very
concentration is
regarded as a constant and not

By rearranging the [H +
] can be found from the pH included
+ there is Also :
for ever an
-




PH
[H +]
-




=
18
kw =
[H +
]
Ka-acid dissociation constant

-
under standard conditions kw is :