1. What is the Acid Dissociation Constant?

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 into its conjugate base and a hydrogen ion.

2. How Does the Calculator Work?

The calculator uses the acid dissociation constant formula:

Where:

• \( K_a \) — Acid dissociation constant (M)
• \( [H^+] \) — Hydrogen ion concentration (M)
• \( [A^-] \) — Conjugate base concentration (M)
• \( [HA] \) — Weak acid concentration (M)

Explanation: The formula expresses the equilibrium between the undissociated acid and its dissociation products in aqueous solution.

3. Importance of Ka Calculation

Details: Ka values are crucial for understanding acid strength, predicting pH of solutions, calculating pKa values, and determining buffer capacities in chemical and biological systems.

4. Using the Calculator

Tips: Enter all concentrations in molarity (M). Ensure [HA] is greater than zero. For weak acids, concentrations should be measured at equilibrium.

5. Frequently Asked Questions (FAQ)

Q1: What does a larger Ka value indicate?
A: A larger Ka value indicates a stronger acid, meaning it dissociates more completely in aqueous solution.

Q2: How is Ka related to pKa?
A: pKa = -log₁₀(Ka). Lower pKa values correspond to stronger acids.

Q3: What are typical Ka values for common acids?
A: Strong acids have Ka > 1, weak acids have Ka < 1. For example, acetic acid Ka ≈ 1.8×10⁻⁵, hydrochloric acid Ka ≈ 10⁷.

Q4: When is this calculation most accurate?
A: This calculation is most accurate for weak acids in dilute solutions where activity coefficients are approximately 1.

Q5: Can this be used for polyprotic acids?
A: For polyprotic acids, separate Ka values must be calculated for each dissociation step (Ka₁, Ka₂, etc.).