Buffer pH Calculator
Calculate buffer solution pH using the Henderson-Hasselbalch equation for acid-base equilibrium
Calculate Buffer pH
Acid dissociation constant (negative log of Ka)
Molar concentration of the weak acid
Molar concentration of the conjugate base
Buffer pH Results
Formula used: pH = pKa + log([A⁻]/[HA])
Calculation: pH = 0 + log(0/0)
pH Scale Reference
Example Calculation
Acetate Buffer Example
Buffer Type: Acid-based (Acetic acid + Sodium acetate)
pKa of acetic acid: 4.8
Acetic acid concentration [CH₃COOH]: 0.1 M
Sodium acetate concentration [CH₃COO⁻]: 0.1 M
Calculation
pH = pKa + log([A⁻]/[HA])
pH = 4.8 + log(0.1/0.1)
pH = 4.8 + log(1)
pH = 4.8 + 0
pH = 4.8
Buffer Types
Acid-based Buffer
Weak acid + its conjugate base
Example: CH₃COOH + CH₃COO⁻
Base-based Buffer
Weak base + its conjugate acid
Example: NH₃ + NH₄⁺
Buffer Applications
Laboratory chemical reactions
Blood pH regulation (bicarbonate)
Biological enzyme reactions
Pharmaceutical formulations
Soil pH management
Buffer Tips
Best buffering occurs when pH ≈ pKa (±1)
Equal concentrations give pH = pKa
Higher concentrations = greater buffer capacity
Temperature affects pKa values
Understanding Buffer pH Calculations
What is a Buffer?
A buffer is a solution that can maintain its pH when small amounts of acid or base are added. It consists of a weak acid and its conjugate base (or a weak base and its conjugate acid) working together to resist pH changes.
Henderson-Hasselbalch Equation
pH = pKa + log([A⁻]/[HA])
For acid-based buffers
Buffer Capacity
Buffer capacity is maximized when the ratio [A⁻]/[HA] = 1, which occurs when pH = pKa. The effective buffering range is typically pKa ± 1 pH unit.
Common Buffer Systems
Phosphate Buffer
H₂PO₄⁻/HPO₄²⁻ (pKa = 7.2)
Used in biological systems
Acetate Buffer
CH₃COOH/CH₃COO⁻ (pKa = 4.8)
Common laboratory buffer
Ammonia Buffer
NH₃/NH₄⁺ (pKa = 9.2)
Basic buffer system
Note: For base-derived buffers, use: pH = 14 - pKb - log([B⁺]/[BOH])