Buffer pH Calculator

Calculate pH of buffer solutions using Henderson-Hasselbalch equation for acid-base buffer systems.

Enter Buffer Data

M
M

Results

Enter buffer data to calculate pH

Henderson-Hasselbalch Equation

Equation

pH = pKa + log([A⁻]/[HA])

  • • [A⁻] = Conjugate base concentration
  • • [HA] = Weak acid concentration
  • • pKa = Acid dissociation constant
  • • log = Base-10 logarithm

Key Points

  • • pH = pKa when [A⁻] = [HA]
  • • Buffer works best near pKa
  • • Effective range: pKa ± 1
  • • 1:1 ratio gives optimal buffering

Common Buffer Systems

Acidic Buffers (pH < 7)

  • • 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 (pH > 7)

  • • 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

Buffer Preparation Tips

Optimal Conditions

  • • Use 1:1 ratio for maximum capacity
  • • Choose pKa close to desired pH
  • • Use high concentrations (0.1-0.5 M)
  • • Consider temperature effects

Common Mistakes

  • • Using wrong pKa value
  • • Ignoring temperature effects
  • • Too dilute solutions
  • • Wrong acid/base pair

Applications

  • • Biological systems
  • • Analytical chemistry
  • • Pharmaceutical formulations
  • • Food preservation