Buffer Capacity Calculator
Calculate buffer capacity and pH stability using Henderson-Hasselbalch equation for acid-base buffer solutions.
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Buffer Capacity
Definition
β = Δn / ΔpH
- • β = Buffer capacity
- • Δn = Moles of acid/base added
- • ΔpH = Change in pH
- • Higher β = better buffer
Henderson-Hasselbalch
pH = pKa + log([A⁻]/[HA])
- • [A⁻] = Conjugate base concentration
- • [HA] = Weak acid concentration
- • Maximum capacity at pH = pKa
- • 1:1 ratio gives best buffering
Common Buffer Systems
Acidic Buffers
- • Acetate: pKa = 4.75, pH range 3.7-5.7
- • Formate: pKa = 3.75, pH range 2.7-4.7
- • Citrate: pKa = 3.13, pH range 2.1-4.1
- • Phosphate: pKa = 2.15, pH range 1.1-3.1
Basic Buffers
- • Ammonia: pKa = 9.25, pH range 8.2-10.2
- • Tris: pKa = 8.07, pH range 7.0-9.0
- • Bicarbonate: pKa = 10.33, pH range 9.3-11.3
- • Phosphate: pKa = 12.32, pH range 11.3-13.3
Factors Affecting Buffer Capacity
Concentration
- • Higher concentration = higher capacity
- • More buffer components
- • Better resistance to pH change
- • Practical limit: solubility
pH Range
- • Maximum at pH = pKa
- • Effective range: pKa ± 1
- • 1:1 ratio gives best capacity
- • Outside range: poor buffering
Temperature
- • pKa changes with temperature
- • Buffer capacity may vary
- • Consider temperature effects
- • Calibrate at working temperature