1. What is Acid Dissociation Constant (Ka)?

The acid dissociation constant (Ka) is a quantitative measure of the strength of an acid in solution. It represents the equilibrium constant for the dissociation reaction of an acid and is related to pKa through the formula Ka = 10^(-pKa).

2. How Does the Calculator Work?

The calculator uses the acid dissociation constant formula:

Where:

• \( Ka \) — Acid dissociation constant (mol/L)
• \( pKa \) — Negative logarithm of Ka (pH units)

Explanation: The pKa value represents the pH at which half of the acid molecules are dissociated. A lower pKa indicates a stronger acid, while a higher pKa indicates a weaker acid.

3. Importance of Ka Calculation

Details: Ka values are crucial in chemistry for predicting acid strength, calculating pH of solutions, understanding buffer systems, and in pharmaceutical applications for drug solubility and absorption.

4. Using the Calculator

Tips: Enter the pKa value in pH units. The calculator will compute the corresponding Ka value. pKa values typically range from -10 (very strong acids) to 50 (very weak acids).

5. Frequently Asked Questions (FAQ)

Q1: What is the relationship between Ka and pKa?
A: pKa is the negative base-10 logarithm of Ka: pKa = -log₁₀(Ka). Therefore, Ka = 10^(-pKa).

Q2: What does a high Ka value indicate?
A: A high Ka value indicates a strong acid that readily donates protons in solution. Strong acids have Ka values greater than 1.

Q3: How does temperature affect Ka values?
A: Ka values are temperature-dependent. For most acids, Ka increases with temperature as dissociation is typically endothermic.

Q4: What are typical Ka values for common acids?
A: Strong acids like HCl have Ka > 10³, weak acids like acetic acid have Ka ≈ 1.8×10⁻⁵, and very weak acids have Ka < 10⁻¹⁰.

Q5: How is Ka used in buffer calculations?
A: Ka is used in the Henderson-Hasselbalch equation to calculate the pH of buffer solutions: pH = pKa + log([A⁻]/[HA]).