Acid-Base and precipitation equilibria Flashcards
1
Q
Buffers are …
A
- a solution prepared by mixing an acid with an appreciable amount of its conjugate base
- between a weak acid and its conjugate base
2
Q
Buffers and pH
A
- have a pH resistant to change
- pH is independent of volume
3
Q
Buffers equations
A
- [H+] = Ka([HB]/[B-])
- -log[H+] = pH
- 10^-pH = [H+]
4
Q
Indicators
A
- are weak acids
- organic dyes
- color depends on [H+]
- indicators usually change over a 2 point pH spread
- Choose an indicator where pKa ≈ pH of the solution at equivalence point
5
Q
Solubility product constant
A
- Ksp
- is sometimes dependent on pH
6
Q
Ksp can be used to calculate …
A
- concentration of one ion at equilibrium
- whether or not the solid will precipitate
- water solubility of the solid
7
Q
The higher the Ksp …
A
the more soluble the solution
8
Q
If Q > Ksp …
A
than precipitation forms
9
Q
If Q < Ksp …
A
than no precipitation forms
10
Q
if Q = Ksp …
A
than solution is saturated
11
Q
Common ion effect
A
- when the solution and solid have an ion in common
- generally describes the solubility of a solute
- Can use Ksp for a slightly soluble electrolyte to estimate its solubility in a solution containing a common ion
12
Q
Ion with smaller Ksp …
A
precipitates first
13
Q
K equation - acids
A
1/Ka = K
14
Q
K equation - bases
A
1/Kb = K
15
Q
when OH- is in the reactants …
A
pH increases and solubility decreases
