1. What is the pH Calculation for Weak Base and Strong Acid?

This calculator determines the pH during titration of a weak base with a strong acid in the buffer region using the Henderson-Hasselbalch equation. It provides accurate pH estimation based on acid-base equilibrium principles.

2. How Does the Calculator Work?

The calculator uses the modified Henderson-Hasselbalch equation:

Where:

• \( pKa \) — Acid dissociation constant (dimensionless)
• \( \text{acid added} \) — Moles of strong acid added (mol)
• \( \text{base remaining} \) — Moles of weak base remaining (mol)

Explanation: This equation applies specifically to the buffer region during titration where both the weak base and its conjugate acid are present in significant amounts.

3. Importance of pH Calculation

Details: Accurate pH calculation is crucial for understanding acid-base equilibria, predicting titration curves, and designing buffer solutions in chemical and biological systems.

4. Using the Calculator

Tips: Enter pKa value, moles of acid added, and moles of base remaining. All values must be valid (acid added ≥ 0, base remaining > 0).

5. Frequently Asked Questions (FAQ)

Q1: When does this equation apply?
A: This equation applies specifically in the buffer region during titration of a weak base with a strong acid, before reaching the equivalence point.

Q2: What are the limitations of this calculation?
A: This calculation assumes ideal behavior, constant temperature, and that the concentrations are within the valid range for the Henderson-Hasselbalch approximation.

Q3: How is pKa related to the weak base?
A: The pKa used here is for the conjugate acid of the weak base being titrated (pKa = 14 - pKb for aqueous solutions at 25°C).

Q4: What happens at the equivalence point?
A: At the equivalence point, this equation no longer applies as the solution contains only the salt of the weak base, and pH is determined by hydrolysis.

Q5: Can this be used for concentrated solutions?
A: For concentrated solutions (>0.1M), activity coefficients should be considered for more accurate results.