Key Points on Titration Curves
A titration curve shows the pH changes during a titration:
- Initial pH: Determined by the starting solution
- Buffer Region: Where pH changes slowly
- Equivalence Point: Where moles of acid = moles of base
- End Point: Visible color change of indicator
Types of Titrations
Different titrations show different curve shapes:
- Strong Acid-Strong Base: Sharp S-curve, equivalence at pH 7
- Weak Acid-Strong Base: Gradual rise, equivalence > pH 7
- Strong Acid-Weak Base: Gradual rise, equivalence < pH 7
- Weak Acid-Weak Base: Very gradual change
Buffer Regions
Understanding buffer regions is crucial:
- Forms when [HA] ≈ [A⁻]
- Maximum buffer capacity at pH = pKa
- Effective range: pH = pKa ± 1
- Buffer capacity depends on total concentration
Indicators and End Points
Choosing the right indicator:
- Indicator range should include equivalence point
- Color change should be sharp and visible
- Multiple indicators may be needed for polyprotic acids
- pH meters provide more accurate results