1. What is the Henderson-Hasselbalch Equation?

The Henderson-Hasselbalch equation relates pH, pKa (acid dissociation constant), and the ratio of concentrations of a weak acid and its conjugate base in solution. It's widely used in chemistry and biochemistry to calculate pH of buffer solutions.

2. How Does the Calculator Work?

The calculator uses the Henderson-Hasselbalch equation:

Where:

• \( pH \) — Negative logarithm of hydrogen ion concentration
• \( pKa \) — Negative logarithm of acid dissociation constant
• \( [base] \) — Concentration of conjugate base (mol/L)
• \( [acid] \) — Concentration of weak acid (mol/L)

Explanation: The equation shows that pH equals pKa when the concentrations of acid and base are equal.

3. Importance of pH Calculation

Details: Accurate pH calculation is crucial for preparing buffer solutions, understanding chemical reactions, and studying biological systems where pH affects molecular structure and function.

4. Using the Calculator

Tips: Enter pKa value, base concentration, and acid concentration in mol/L. All values must be valid (acid concentration > 0).

5. Frequently Asked Questions (FAQ)

Q1: What is the relationship between pKa and pH?
A: pKa is a constant for a given acid at a specific temperature, while pH depends on the concentrations of acid and base in solution.

Q2: What are typical pKa values?
A: Strong acids have low or negative pKa values, while weak acids typically have pKa between 2-12.

Q3: When is the Henderson-Hasselbalch equation valid?
A: It works best when the concentrations of acid and base are much larger than the concentration of H+ or OH- ions.

Q4: What are common buffer systems?
A: Common buffers include acetic acid/acetate (pKa 4.76), phosphate (pKa 7.21), and Tris (pKa 8.07).

Q5: How does temperature affect pKa?
A: pKa values are temperature-dependent, so calculations should use pKa values measured at the same temperature as the solution.