1. What is the Buffer pH Equation After Adding NaOH?

The buffer pH equation calculates the new pH of a buffer solution after adding a strong base like NaOH. It's based on the Henderson-Hasselbalch equation and accounts for the consumption of weak acid and formation of conjugate base.

2. How Does the Calculator Work?

The calculator uses the buffer pH equation:

Where:

• \( pKa \) — Acid dissociation constant (dimensionless)
• \( [A⁻] \) — Initial concentration of conjugate base (mol/L)
• \( [HA] \) — Initial concentration of weak acid (mol/L)
• \( added \) — Amount of NaOH added (mol)

Explanation: The equation shows how adding NaOH converts HA to A⁻, changing the ratio in the logarithmic term and thus the pH.

3. Importance of Buffer pH Calculation

Details: Calculating pH changes in buffer solutions is crucial for understanding buffer capacity, designing biological experiments, and maintaining stable pH conditions in chemical and biochemical systems.

4. Using the Calculator

Tips: Enter pKa value, initial concentrations of conjugate base and weak acid, and the amount of NaOH added. Ensure [HA] > added NaOH for valid calculation.

5. Frequently Asked Questions (FAQ)

Q1: Why does adding NaOH change the buffer pH?
A: NaOH reacts with the weak acid (HA) to form conjugate base (A⁻), changing the [A⁻]/[HA] ratio in the Henderson-Hasselbalch equation.

Q2: What happens if I add too much NaOH?
A: If added NaOH exceeds [HA], the buffer capacity is exceeded, and the solution behaves like a weak base solution, requiring different calculations.

Q3: Can this equation be used for other strong bases?
A: Yes, the equation works for any strong base that completely converts HA to A⁻, such as KOH or LiOH.

Q4: What are typical pKa values for common buffers?
A: Acetic acid: 4.76, Phosphoric acid (pKa2): 7.20, Tris: 8.06, Bicarbonate: 6.35/10.33.

Q5: How accurate is this calculation?
A: The calculation assumes ideal behavior and constant activity coefficients. For precise work, activity corrections may be needed.