1. What is the pH Calculation at Equivalence Point?

This calculator determines the pH at the equivalence point for the titration of a weak base (methylamine) with a strong acid. At equivalence, the solution contains the conjugate acid of the weak base, and pH is calculated from hydrolysis of this conjugate acid.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( pK_w \) — Negative logarithm of water ionization constant (typically 14.00 at 25°C)
• \( pK_b \) — Negative logarithm of base dissociation constant
• \( C \) — Concentration of the weak base solution (mol/L)

Explanation: This formula accounts for the hydrolysis of the conjugate acid formed at the equivalence point of weak base-strong acid titration.

3. Importance of pH Calculation

Details: Accurate pH calculation at equivalence point is crucial for understanding titration curves, selecting appropriate indicators, and determining the exact endpoint in acid-base titrations.

4. Using the Calculator

Tips: Enter pKw (typically 14.00), pKb of the weak base (3.36 for methylamine), and concentration in mol/L. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why is this formula specific for weak base-strong acid titration?
A: Because at equivalence point, the solution contains the conjugate acid of the weak base, which hydrolyzes to give an acidic solution.

Q2: What is the typical pKb value for methylamine?
A: Methylamine has a pKb value of approximately 3.36 at 25°C.

Q3: Does temperature affect the calculation?
A: Yes, pKw changes with temperature (13.99 at 0°C, 13.68 at 50°C), which affects the pH calculation.

Q4: What assumptions does this formula make?
A: It assumes ideal behavior, negligible dilution effects, and that the concentration C represents the initial concentration of the weak base.

Q5: Can this calculator be used for other weak bases?
A: Yes, by entering the appropriate pKb value for any weak base being titrated with a strong acid.