Monoprotic Acid-Base Equilibria

Question 1

pH of high concentrations strong acids or bases (≥10-6 M)

Answer 1

pH or pOH is
obtained directly from the formal concentration of
acid or base

Question 2

pH of low concentrations strong acids or bases (<10-6 M)

Answer 2

Use the systematic treatment of equilibrium.

Question 3

pH of weak acids

Answer 3

HA ⇌ H+ + A-
where [H+] = [A-] = x, and [HA] = F - x

Question 4

pH of weak bases

Answer 4

B + H2O ⇄ BH+ + OH-
Kb = x2/(F - x)
where [OH-] = [BH+] = x, and [B] = F - x

Question 5

Buffers

Answer 5

A buffer is a mixture of a weak acid and its conjugate base
resists changes in pH because it reacts with added acid or base

Question 6

Henderson-Hasselbalch
equation

Answer 6

pH= pKa + log([A-]/[HA])

Question 7

conjugate base of a weak acid

Answer 7

a weak base
-if one member of a conjugate pair is weak, so is its conjugate

Question 8

The weaker the acid,

Answer 8

the stronger the base

Question 9

When a strong acid (or base) is added to a weak base
(or acid)

Answer 9

they react nearly completely

Question 10

buffer capacity increases

Answer 10

as the concentration of
buffer increases

Question 11

The pH of a buffer

Answer 11

is nearly independent of dilution

Question 12

The maximum buffer capacity for a solution

Answer 12

is at pH =
pKa, and the useful range is pH = pKa ± 1

Question 13

Choosing a buffer system

Answer 13

Choose a weak acid /conjugate base system with a pKa ±1 of desired pH.
* Look at the exponent in the Ka value. It should be close to
the pH desired