Calculation Results

Buffer pH: 5.363

[A⁻]/[HA] Ratio: 4.000

log₁₀([A⁻]/[HA]): 0.602

Formula: pH = pKa + log₁₀([A⁻]/[HA])

5.363 = 4.76 + log₁₀(0.08/0.02)

About Buffer pH Calculations

Buffer solutions maintain stable pH levels by resisting changes when small amounts of acid or base are added. The Henderson-Hasselbalch equation calculates the pH of buffers using the pKa value and concentration ratio of conjugate base to weak acid.

Calculation Steps:

Determine pKa value for the weak acid (e.g., 4.76 for acetic acid)
Measure concentrations of conjugate base ([A⁻]) and weak acid ([HA])
Calculate concentration ratio [A⁻]/[HA]
Compute log₁₀ of the ratio
Add pKa to the logarithmic value

Examples:

Acetate Buffer (1:1 ratio):

pKa = 4.76, [A⁻] = 0.05M, [HA] = 0.05M

pH = 4.76 + log₁₀(1) = 4.76

Phosphate Buffer (2:1 ratio):

pKa = 7.20, [A⁻] = 0.04M, [HA] = 0.02M

pH = 7.20 + log₁₀(2) = 7.50

Common Buffer Systems:

Buffer	pKa	Effective Range
Acetic Acid/Acetate	4.76	3.8-5.8
Phosphate (pKa₂)	7.20	6.2-8.2
Tris/HCl	8.08	7.0-9.0

Important Notes:

Valid when [A⁻] and [HA] are significantly greater than [H⁺] and [OH⁻]
Ionic strength and temperature affect pKa values
Maximum buffering capacity occurs when pH = pKa
Measure concentrations accurately using validated methods

Buffer pH Calculator

Calculation Results

About Buffer pH Calculations

Calculation Steps:

Examples:

Common Buffer Systems:

Important Notes:

Buffer Capacity Visualization

Frequently Asked Questions

Why is my calculated pH different from measured pH?

What if my ratio is negative or zero?

When should I use alternative equations?

Formulas & Assumptions

References

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Buffer pH Calculator Henderson Hasselbalch Equation

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