1. What is pH at Equivalence Point?

The pH at equivalence point in acid-base titrations depends on the nature of the acid and base being titrated. For strong acid-strong base titrations, the equivalence point occurs at pH 7. For weak acid-strong base or weak base-strong acid titrations, the pH is calculated using the formula: ½ pKw + ½ pKa.

2. How Does the Calculator Work?

The calculator uses the following formulas:

Where:

• pH — pH value at equivalence point (dimensionless)
• pKw — Negative logarithm of water ion product (dimensionless)
• pKa — Negative logarithm of acid dissociation constant (dimensionless)

Explanation: The calculation accounts for the different behavior of strong and weak electrolytes at the equivalence point of titration.

3. Importance of pH Calculation

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

4. Using the Calculator

Tips: Select the titration type, enter pKw value (typically 14.00 at 25°C), and for weak acid/base titrations, provide the pKa value. All values must be valid positive numbers.

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 pH of 7 at equivalence point.

Q2: What is the typical value of pKw?
A: At 25°C, pKw is 14.00, but it varies with temperature. The calculator allows you to input different pKw values for different conditions.

Q3: How do I determine pKa for weak acids/bases?
A: pKa values are typically found in reference tables or determined experimentally. They represent the acid strength of the compound.

Q4: Are there exceptions to these formulas?
A: These formulas work for monoprotic acids and bases. For polyprotic systems, the calculation becomes more complex and depends on which equivalence point is being considered.

Q5: Why is the pH different for weak acid/strong base vs weak base/strong acid?
A: The formulas are essentially the same (½ pKw + ½ pKa), but the interpretation differs based on whether you're dealing with the conjugate acid or base at the equivalence point.