Calculate Ph Of Buffer After Adding Strong Base

Buffer pH Equation After Base Addition:

\[ pH_{new} = pK_a + \log\left( \frac{[A^-] + added}{[HA] - added} \right) \]

pKa:

[A⁻] (Conjugate Base Concentration):

mol

[HA] (Weak Acid Concentration):

mol

Added Base:

mol

pH_new (dimensionless):

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1. What is Buffer pH Calculation After Base Addition?

The buffer pH equation calculates the new pH of a buffer solution after adding a strong base. 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:

\[ pH_{new} = pK_a + \log\left( \frac{[A^-] + added}{[HA] - added} \right) \]

Where:

\( pK_a \) — Acid dissociation constant (dimensionless)
\( [A^-] \) — Initial conjugate base concentration (mol)
\( [HA] \) — Initial weak acid concentration (mol)
\( added \) — Amount of strong base added (mol)

Explanation: The equation calculates the new pH based on the ratio of conjugate base to weak acid after the strong base reacts with the weak acid.

3. Importance of Buffer pH Calculation

Details: Accurate pH calculation is crucial for understanding buffer capacity, predicting solution behavior after base addition, and designing effective buffer systems for chemical and biological applications.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: Why does the pH change when adding base to a buffer?
A: The strong base reacts with the weak acid, converting HA to A⁻, which changes the [A⁻]/[HA] ratio and thus the pH according to the Henderson-Hasselbalch equation.

Q2: What happens if I add more base than the buffer capacity?
A: If added base exceeds the weak acid concentration ([HA]), the buffer capacity is exceeded, and the pH will rise dramatically as the solution behaves like a strong base solution.

Q3: Can this equation be used for acid addition?
A: For acid addition, the equation becomes: pH_new = pKa + log(([A⁻] - added)/([HA] + added))

Q4: What are the limitations of this calculation?
A: This assumes ideal behavior, constant temperature, and that the added base completely reacts with the weak acid. It may not account for dilution effects or activity coefficients.

Q5: How accurate is this calculation for real buffer systems?
A: For most practical purposes with dilute solutions, this calculation provides good estimates. For precise work, consider activity coefficients and possible secondary equilibria.