Weak Acid Ionization

Titration Curve: pH vs Volume of Base Added

Base Added: 0.00 mL

Current pH: 0.00

pH Scale & Indicator Color

Indicator Transition Range: 8.2-10.0

Current Color:

Molecular View: Acid Ionization Animation

HA (undissociated) H⁺ (proton) A⁻ (conjugate base)

Current Values

[HA] 0.00 M

[H⁺] 0.00 M

[A⁻] 0.00 M

Ionization Degree α 0.00%

Ka (Acid Constant) 0.00

pKa = -log Ka 0.00

% Ionization 0.00%

Buffer Capacity 0.00

Acid Parameters & Titration Controls

Weak Acid Parameters

Acid Concentration [HA]₀: 0.10 M Acid Dissociation Constant Ka: 1.80e-5

Value is log₁₀(Ka), range: 10⁻¹⁰ to 10⁻²

Initial Acid Volume: 50 mL

Titrant (Strong Base) Parameters

Base Concentration [OH⁻]: 0.10 M Maximum Base Volume to Add: 100 mL Base Type:

Acid-Base Indicators

Indicator:

Acid Color: Base Color:

Titration Controls

Volume of Base Added: 0.00 mL Animation Speed: 1.0x

Quick Presets

Weak Acid Ionization Equations

Ionization Equation: HA ⇌ H⁺ + A⁻

Acid Dissociation Constant: Ka = [H⁺][A⁻]/[HA]

pH Definition: pH = -log[H⁺]

Ionization Degree: α = [H⁺]/[HA]₀ = √(Ka/[HA]₀)

H⁺ Concentration (weak acid): [H⁺] = √(Ka × [HA]₀)

pKa Relationship: pKa = -log Ka, pH = pKa at half-equivalence

Henderson-Hasselbalch: pH = pKa + log([A⁻]/[HA])

What is Weak Acid Ionization?

Weak acids are acids that do not completely dissociate in water, establishing an equilibrium between the undissociated acid molecules (HA) and their ions (H⁺ and A⁻). Unlike strong acids which dissociate completely, weak acids only partially ionize, characterized by their acid dissociation constant Ka. Common examples include acetic acid (CH₃COOH) in vinegar, formic acid (HCOOH) in ant venom, and carbonic acid (H₂CO₃) in carbonated beverages.

Acid Strength and Ka

Ka Value: The acid dissociation constant Ka quantifies acid strength. Larger Ka values indicate stronger acids.
pKa Scale: pKa = -log(Ka) provides a convenient scale. Lower pKa means stronger acid.
Concentration Effect: Percent ionization increases with dilution (Ostwald's dilution law).

Acid-Base Titration

Titration Process: Weak acid titrated with strong base.
Equivalence Point: pH > 7 for weak acid-strong base.
Half-Equivalence Point: pH = pKa when [A⁻] = [HA].

Buffer Solutions

Buffer Action: Solutions resist pH changes. Maximum capacity at pH = pKa.
Henderson-Hasselbalch: pH = pKa + log([A⁻]/[HA]).

Acid-Base Indicators

Indicator Mechanism: Weak acids/bases with different colored forms.
Choosing Indicators: Select based on equivalence point pH.

Ostwald's Dilution Law

Describes how ionization degree varies with concentration: α ≈ √(Ka/c).

Real-World Applications

Biological systems, food chemistry, industrial processes, environmental chemistry, analytical chemistry.

Polyprotic Acids

Acids with multiple dissociable protons, each with its own Ka value.