⚗️ Henderson-Hasselbalch Equation & Buffer Capacity
Henderson-Hasselbalch Buffer Calculator
Compute buffer solution pH, solve for required $[A^-]/[HA]$ conjugate ratio to achieve a target pH, and evaluate Van Slyke buffer capacity ($\beta$).
🧪 Acetate Buffer ($pK_a = 4.76$)
🩸 Phosphate PBS ($pK_a = 7.21$)
🧬 Tris-HCl ($pK_a = 8.06$)
🫁 Bicarbonate ($pK_a = 6.35$)
🍋 Citrate ($pK_a = 3.13$)
Buffer System Parameters
M (Molar)
M (Molar)
Resulting Buffer Solution pH
pH = 7.21
Buffer Capacity ($\beta$)
0.115 M/pH
Total Buffer Conc
0.200 M
Optimal Range
6.21 – 8.21
💡 Formula Calculation:
$$\text{pH} = 7.21 + \log_{10}(0.10 / 0.10) = 7.21 + 0 = 7.21$$
The Henderson-Hasselbalch Equation
For a weak acid equilibrium $HA \rightleftharpoons H^+ + A^-$:
$$\text{pH} = pK_a + \log_{10}\left(\frac{[A^-]}{[HA]}\right)$$
- Maximum Buffering Capacity: Occurs when $[A^-] = [HA]$, meaning $\text{pH} = pK_a$.
- Effective Buffer Range: Typically $pK_a \pm 1.0\text{ pH units}$.
- Van Slyke Buffer Capacity ($\beta$): $$\beta = 2.303 \times C_{\text{total}} \times \frac{[H^+] K_a}{([H^+] + K_a)^2}$$