1. What is the Phosphate Buffer System?

The phosphate buffer system is an important biological buffer that helps maintain pH in intracellular fluids and the renal tubules. It consists of dihydrogen phosphate (H₂PO₄⁻) as the weak acid and hydrogen phosphate (HPO₄²⁻) as the conjugate base.

2. How Does the Calculator Work?

The calculator uses the Henderson-Hasselbalch equation:

Where:

• \( pH \) — Resulting pH of the buffer solution
• \( pKa \) — Acid dissociation constant (typically 7.2 for phosphate buffer)
• \( [PO_4] \) — Concentration of the basic form (HPO₄²⁻)
• \( [HPO_4] \) — Concentration of the acidic form (H₂PO₄⁻)

Explanation: The equation calculates the pH of a buffer solution based on the ratio of conjugate base to weak acid concentrations.

3. Importance of pH Calculation in Buffers

Details: Accurate pH calculation is crucial for preparing buffer solutions in biochemical experiments, pharmaceutical formulations, and maintaining physiological conditions in biological systems.

4. Using the Calculator

Tips: Enter the pKa value (typically 7.2 for phosphate buffer), concentrations of both buffer components in mol/L. All values must be valid (concentrations > 0).

5. Frequently Asked Questions (FAQ)

Q1: What is the typical pKa value for phosphate buffer?
A: The phosphate buffer system has a pKa of approximately 7.2 at 25°C, making it ideal for buffering in the physiological pH range.

Q2: Why is the phosphate buffer important biologically?
A: It's a major intracellular buffer and plays a crucial role in renal acid-base regulation and urine acidification.

Q3: What is the effective buffering range of phosphate buffer?
A: Phosphate buffer is most effective in the pH range of approximately 6.2-8.2 (pKa ± 1).

Q4: How does temperature affect the pKa of phosphate buffer?
A: The pKa of phosphate buffer decreases slightly with increasing temperature (approximately -0.0028 units per °C).

Q5: Can phosphate buffer be used in all biological applications?
A: While widely used, phosphate buffer may interfere with some enzymatic reactions and phosphate-dependent processes, so alternative buffers may be needed in specific cases.