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- Point 1:
Start of the Titration
- Only HA; no NaOH added yet.
- pH determined by "strength" of HA.
- How does Ka influence pH?
- Region 2:
Between the Start and the Equivalence Point
- HA and NaOH react to form more A-.
- pH slowly increases. Why slowly?
- ÔHalf equivalence pointÕ is exactly midway between
start and equivalence point.
- Point 3:
The Equivalence Point
- Enough NaOH has been added to react with all HA
moles NaOH added = moles HA initially present
No NaOH, HA remain (rxn
complete)
Only NaA + water remain
- pH is determined by the strength of A-.
- How does Ka of HA influence pH here?
- Region 4:
After the Equivalence Point
- More NaOH is added, but there is no HA for rxn.
- The NaOH simply raises the pH.
- Problem: Consider the titrations of 0.0050 mole HA and 0.0050
mole HCl
HA + NaOH --> H2O + NaA
HCl + NaOH --> H2O + NaCl
Account for
differences in
- Initial pH
- Equivalence point (pH, volume NaOH)
- Half equivalence point location (pH, volume NaOH)
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