1. What is the Henderson-Hasselbalch Equation?

The Henderson-Hasselbalch equation relates the pH of a buffer solution to the pKa of the weak acid and the concentrations of the weak acid and its conjugate base. It's fundamental in chemistry and biochemistry for preparing buffer solutions.

2. How Does the Calculator Work?

The calculator uses the Henderson-Hasselbalch equation:

Where:

• \( pH \) — The calculated pH of the solution
• \( pKa \) — The acid dissociation constant of the weak acid
• \( [\text{conjugate}] \) — Concentration of conjugate base (M)
• \( [\text{weak}] \) — Concentration of weak acid (M)

Explanation: The equation shows that buffer pH depends on the ratio of conjugate base to weak acid concentrations, not their absolute values.

3. Importance of Buffer pH Calculation

Details: Accurate pH calculation is crucial for preparing effective buffer solutions used in chemical reactions, biological systems, and laboratory experiments where maintaining stable pH is essential.

4. Using the Calculator

Tips: Enter the pKa value of your weak acid, the concentration of conjugate base, and the concentration of weak acid. All concentrations must be in molarity (M) and greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: What is the buffer range?
A: A buffer is most effective when pH = pKa ± 1. Outside this range, buffering capacity decreases significantly.

Q2: What are common buffer systems?
A: Common systems include acetic acid/acetate (pKa 4.76), phosphate (pKa 7.21), and Tris (pKa 8.07).

Q3: Does temperature affect the calculation?
A: Yes, pKa values are temperature-dependent. Use pKa values measured at your working temperature.

Q4: What if my ratio is 1:1?
A: When [conjugate] = [weak], pH = pKa since log(1) = 0.

Q5: Can I use this for polyprotic acids?
A: For polyprotic acids, use the pKa closest to your desired pH range and consider only that equilibrium.