1. What is pKa from Titration Curve?

The pKa is the pH at which half of the acid molecules are deprotonated. In a titration curve, this corresponds to the pH at the half-equivalence point, where half the volume needed to reach the equivalence point has been added.

2. How Does the Calculator Work?

The calculator uses the fundamental relationship:

Explanation: At the half-equivalence point, the concentrations of the acid and its conjugate base are equal, making pH = pKa by the Henderson-Hasselbalch equation.

3. Importance of pKa Calculation

Details: Knowing pKa values is essential for understanding acid-base chemistry, predicting protonation states, and designing buffer systems in chemistry and biochemistry.

4. Using the Calculator

Tips: Enter the pH value at the half-equivalence point from your titration curve. The value must be between 0-14 pH units.

5. Frequently Asked Questions (FAQ)

Q1: Why does pKa equal pH at half equivalence?
A: At half equivalence, [HA] = [A⁻], so the Henderson-Hasselbalch equation simplifies to pH = pKa + log(1) → pH = pKa.

Q2: How accurate is this method?
A: Very accurate for monoprotic acids when the titration curve is properly obtained and the half-equivalence point is correctly identified.

Q3: Can this be used for polyprotic acids?
A: Yes, but each proton has its own pKa and corresponding half-equivalence point in the titration curve.

Q4: What affects the precision of pKa determination?
A: Temperature, ionic strength, and accurate determination of the equivalence point all affect precision.

Q5: How does temperature affect pKa?
A: pKa values are temperature-dependent, so results should specify the temperature at which the titration was performed.