1. What is the Dissociation Constant of a Weak Acid?

Definition: The dissociation constant (Kₐ) is a quantitative measure of the strength of a weak acid in solution, representing its tendency to donate protons.

Purpose: It helps chemists predict the extent of acid dissociation and calculate pH values for weak acid solutions.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( K_a \) — Acid dissociation constant
• \( [H^+] \) — Concentration of hydrogen ions (mol/m³)
• \( [A^-] \) — Concentration of anions (mol/m³)
• \( [HA] \) — Concentration of undissociated weak acid (mol/m³)

Explanation: The product of the hydrogen ion and anion concentrations is divided by the concentration of the undissociated acid.

3. Importance of Dissociation Constant

Details: Kₐ values help predict acid strength (smaller Kₐ = weaker acid), calculate pH, and understand buffer systems in chemistry and biology.

4. Using the Calculator

Tips: Enter the concentrations of hydrogen ions, anions, and undissociated weak acid in mol/m³. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What are typical Kₐ values for weak acids?
A: Weak acids typically have Kₐ values between 10⁻² and 10⁻¹⁰. For example, acetic acid has Kₐ = 1.8 × 10⁻⁵.

Q2: How does temperature affect Kₐ?
A: Kₐ is temperature-dependent, generally increasing with temperature as dissociation is usually endothermic.

Q3: What's the relationship between Kₐ and pKₐ?
A: pKₐ = -log₁₀(Kₐ). Lower pKₐ values indicate stronger acids.

Q4: Can this calculator be used for strong acids?
A: No, strong acids are considered 100% dissociated in water, making Kₐ calculations unnecessary.

Q5: How do I convert between mol/m³ and mol/L?
A: 1 mol/m³ = 0.001 mol/L (or M). Multiply mol/m³ values by 0.001 to get molarity.