Week 11

Question 1

NaCN

Answer 1

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)

Question 2

NH4Cl

Answer 2

Salt of NH4OH (weak base) and HCl (strong acid)
* Acid “wins”: pH < 7 and reaction is
* H2O(aq) + NH4+(aq) ⟺ NH3(aq) + H3O+(aq)

Question 3

If you add the salt of an acid to a solution of the same acid ….

Answer 3

then the equilibrium will shift towards neutral

Question 4

A buffer solution

Answer 4

an acid or a base aqueous solution consisting of a mixture of a weak acid and its conjugate base, or vice versa

Question 5

Buffer capacity

Answer 5

Amount of strong acid or base that can be added without causing significant pH change.
* Depends on amount of acid & conjugate base in solution

Question 6

Most effective buffers have acid/base ratio…

Answer 6

less than 10 and more than 0.1 ⇒ pH range is ±1

Question 7

pH control is essential because

Answer 7

biochemical reactions are very sensitive to pH

Question 8

Human blood is slightly…

Answer 8

Basic - pH ≈ 7.39 – 7.45

Question 9

Deviations from normal blood pH

Answer 9

pH < 7.2, “acidosis”; pH > 7.6, “alkalosis”.

Death occurs if pH < 6.8 or > 7.8

Question 10

To make up a buffer, we need pH…

Answer 10

near pKa

Question 11

Equivalence point

Answer 11

when the amount of added base = initial amount of acid:

Question 12

strong acids…

Answer 12

completely dissociate in solution