1. What is pH at Equivalence Point?

The pH at equivalence point in a titration is the pH value when the amount of titrant added is stoichiometrically equivalent to the amount of analyte present. It depends on the strengths of the acid and base involved in the titration.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( pH \) — pH value (dimensionless)
• \( pK_w \) — Water ion product (dimensionless)
• \( pK_a \) — Acid dissociation constant (dimensionless)

Explanation: The specific formula used depends on whether strong or weak acids/bases are involved in the titration:

• Strong acid + Strong base: pH = 7
• Weak acid + Strong base: pH = 7 + ½pKa - ½pKw
• Strong acid + Weak base: pH = 7 - ½pKa + ½pKw

3. Importance of pH Calculation

Details: Calculating the pH at equivalence point is crucial for determining the appropriate indicator to use in acid-base titrations and for understanding the titration curve behavior.

4. Using the Calculator

Tips: Enter pKa value for weak acids/bases, pKw value (default is 14.0 for water at 25°C), and select the appropriate acid and base types from the dropdown menus.

5. Frequently Asked Questions (FAQ)

Q1: Why is pH = 7 for strong acid-strong base titration?
A: Because the salt formed is neutral and doesn't undergo hydrolysis, resulting in a neutral solution at equivalence point.

Q2: What is the typical pKw value?
A: For water at 25°C, pKw = 14.0. This value changes with temperature.

Q3: When is pKa required?
A: pKa is required when either the acid or base involved in the titration is weak, as it determines the extent of hydrolysis.

Q4: What about weak acid-weak base titrations?
A: These are more complex and the pH calculation depends on the relative strengths of both acid and base. The calculator provides "N/A" for such cases.

Q5: How does temperature affect the calculation?
A: Temperature affects pKw value. For accurate results, use the appropriate pKw value for the temperature at which the titration is performed.