Questions. What is a strong acid? What is a weak acid? Write expression for pH HX ( aq ) + H 2 O (l) X - ( aq ) +H 3 O + For a strong acid like one above, what can you say about the concentration of [HX] and [ H 3 O + ]?. Water dissociation constant, K w. K w = [H 3 O + ] x [OH - ]
For a strong acid like one above, what can you say about the concentration of [HX] and [H3O+]?
Kw = [H3O+] x [OH-]
Increases with increased temperature
At 25 deg Kw = 1X10-14
Do not fully dissociate so:
CH3COOH + H2O n CH3COO- + H3O+
As they are in equilibrium, when they are diluted water concentration is increased and there is a shift to the right to compensate.
This means predicting pH increase is harder.
But water is a solvent so
So Ka =
and pH = -log[H3O+]
Now try Exercise 13C
[H3O+] = [A-]
Ka x [HA]
As the strength of acid increase
Ka gets bigger
Conjugate base gets weaker