Week 11 Flashcards
NaCN
The salt of NaOH (strong base) and HCN (weak acid).
* The base “wins”: pH > 7
Overall reaction is:
* H2O(aq) + CN-(aq) ⟺ OH-(aq) + HCN(aq)
NH4Cl
Salt of NH4OH (weak base) and HCl (strong acid)
* Acid “wins”: pH < 7 and reaction is
* H2O(aq) + NH4+(aq) ⟺ NH3(aq) + H3O+(aq)
If you add the salt of an acid to a solution of the same acid ….
then the equilibrium will shift towards neutral
A buffer solution
an acid or a base aqueous solution consisting of a mixture of a weak acid and its conjugate base, or vice versa
Buffer capacity
Amount of strong acid or base that can be added without causing significant pH change.
* Depends on amount of acid & conjugate base in solution
Most effective buffers have acid/base ratio…
less than 10 and more than 0.1 ⇒ pH range is ±1
pH control is essential because
biochemical reactions are very sensitive to pH
Human blood is slightly…
Basic - pH ≈ 7.39 – 7.45
Deviations from normal blood pH
pH < 7.2, “acidosis”; pH > 7.6, “alkalosis”.
Death occurs if pH < 6.8 or > 7.8
To make up a buffer, we need pH…
near pKa
Equivalence point
when the amount of added base = initial amount of acid:
strong acids…
completely dissociate in solution