Sodium Phosphate Buffer Calculator Anhydrous

Henderson-Hasselbalch Equation:

\[ pH = pKa2 + \log\left(\frac{[Na₂HPO₄]}{[NaH₂PO₄]}\right) \]

Calculated pH:

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1. What is Sodium Phosphate Buffer?

Sodium phosphate buffer is a commonly used buffer system in biological and chemical applications. It consists of two components: monosodium phosphate (NaH₂PO₄) and disodium phosphate (Na₂HPO₄) that work together to maintain stable pH levels.

2. How Does the Calculator Work?

The calculator uses the Henderson-Hasselbalch equation:

\[ pH = pKa2 + \log\left(\frac{[Na₂HPO₄]}{[NaH₂PO₄]}\right) \]

Where:

\( pH \) — Resulting pH of the buffer solution
\( pKa2 \) — Acid dissociation constant for phosphoric acid (typically 7.2)
\( [Na₂HPO₄] \) — Concentration of disodium phosphate (mol/L)
\( [NaH₂PO₄] \) — Concentration of monosodium phosphate (mol/L)

Explanation: The equation calculates the pH based on the ratio of the basic to acidic forms of phosphate in the buffer system.

3. Importance of Phosphate Buffer

Details: Phosphate buffers are widely used in biological research, pharmaceutical preparations, and clinical diagnostics due to their excellent buffering capacity in the physiological pH range (6.0-8.0).

4. Using the Calculator

Tips: Enter the pKa2 value (typically 7.2 for phosphoric acid), concentrations of both buffer components in mol/L. All concentration values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical pKa2 value for phosphoric acid?
A: The second dissociation constant (pKa2) for phosphoric acid is typically 7.2 at 25°C.

Q2: What is the effective buffering range for phosphate buffers?
A: Phosphate buffers are most effective in the pH range of 6.0-8.0, with optimal buffering around pH 7.2.

Q3: Can I use this calculator for hydrated salts?
A: This calculator is designed for anhydrous salts. For hydrated forms, you must account for the water of hydration in your calculations.

Q4: Why are phosphate buffers commonly used in biological applications?
A: Phosphate buffers are non-toxic, compatible with biological systems, and provide good buffering capacity in the physiological pH range.

Q5: How does temperature affect the pKa2 value?
A: The pKa2 value decreases slightly with increasing temperature. For precise work, use pKa values measured at your working temperature.