pH Calculation Titration

Henderson-Hasselbalch Equation:

\[ pH = pKa + \log\left(\frac{\text{titrant}}{\text{analyte}}\right) \]

Acid Dissociation Constant (pKa):

(dimensionless)

Titrant Concentration:

mol/L

Analyte Concentration:

mol/L

pH Value:

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is the Henderson-Hasselbalch Equation?

The Henderson-Hasselbalch equation is used to estimate the pH of a buffer solution during titration. It relates pH, pKa (acid dissociation constant), and the ratio of concentrations of the conjugate base to weak acid.

2. How Does the Calculator Work?

The calculator uses the Henderson-Hasselbalch equation:

\[ pH = pKa + \log\left(\frac{\text{titrant}}{\text{analyte}}\right) \]

Where:

\( pH \) — pH value (dimensionless)
\( pKa \) — Acid dissociation constant (dimensionless)
\( \text{titrant} \) — Concentration of titrant (mol/L)
\( \text{analyte} \) — Concentration of analyte (mol/L)

Explanation: The equation is particularly useful in the buffer region of a titration curve where the ratio of conjugate base to weak acid is between 0.1 and 10.

3. Importance of pH Calculation in Titration

Details: Accurate pH calculation is crucial for understanding titration curves, determining equivalence points, and predicting buffer capacity in chemical and biological systems.

4. Using the Calculator

Tips: Enter pKa value, titrant concentration, and analyte concentration. All values must be valid positive numbers. The calculator is most accurate within the buffer region.

5. Frequently Asked Questions (FAQ)

Q1: When is the Henderson-Hasselbalch equation valid?
A: The equation is valid when the concentrations of acid and conjugate base are much larger than the concentration of H+ or OH- ions, typically in the buffer region.

Q2: What is the buffer region in titration?
A: The buffer region is the flat portion of the titration curve where pH changes slowly with addition of titrant, typically ±1 pH unit around the pKa value.

Q3: What are the limitations of this equation?
A: The equation assumes ideal behavior, constant temperature, and may not be accurate for very dilute solutions or strong acid/strong base titrations.

Q4: How does temperature affect the calculation?
A: Temperature affects both pKa values and the autoionization constant of water (Kw), which can influence pH calculations.

Q5: Can this equation be used for polyprotic acids?
A: For polyprotic acids, the equation can be applied to each dissociation step separately, considering the appropriate pKa value for each protonation state.