Home
Back
Phosphate Buffer Equation:
| From: | To: |
The phosphate buffer equation calculates the ratio of base to acid concentrations needed to achieve a specific pH in a phosphate buffer system. It's based on the Henderson-Hasselbalch equation and is widely used in biochemistry and laboratory preparations.
The calculator uses the phosphate buffer equation:
Where:
Explanation: The equation shows how the ratio of conjugate base to acid changes with pH relative to the pKa of the buffer system.
Details: Accurate buffer preparation is essential for maintaining stable pH in biological systems, chemical reactions, and laboratory experiments. The phosphate buffer system is particularly important in physiological systems.
Tips: Enter the desired pH and the pKa value (typically 7.2 for phosphate buffer at 25°C). The calculator will provide the molar ratio of base to acid needed to achieve this pH.
Q1: What is the typical pKa for phosphate buffer?
A: The second pKa of phosphoric acid (H₂PO₄⁻/HPO₄²⁻ system) is 7.2 at 25°C, which is most commonly used for physiological buffers.
Q2: How does temperature affect the pKa?
A: pKa values are temperature-dependent. For phosphate buffer, pKa decreases by about 0.0028 units per °C increase in temperature.
Q3: What are common phosphate buffer components?
A: Typically monobasic (KH₂PO₄ or NaH₂PO₄) and dibasic (K₂HPO₄ or Na₂HPO₄) phosphate salts are used.
Q4: What is the effective buffer range?
A: Phosphate buffers are most effective in the pH range of about 6.2 to 8.2 (pKa ± 1).
Q5: How do I prepare the actual buffer solution?
A: Use the calculated ratio to mix appropriate amounts of acid and base components, then verify pH with a calibrated pH meter.