1. What is Percent Dissociation?

Definition: Percent dissociation measures what percentage of water molecules have dissociated into hydrogen (H⁺) and hydroxide (OH⁻) ions at a given temperature.

Purpose: It helps chemists understand the extent of water autoionization and calculate pH or pOH values in aqueous solutions.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( \%D \) — Percent dissociation (%)
• \( \alpha \) — Degree of dissociation (dimensionless, between 0 and 1)

Explanation: The degree of dissociation (α) is simply multiplied by 100 to convert it to a percentage.

3. Importance of Percent Dissociation

Details: In pure water at 25°C, only about 1 in 10 million molecules are dissociated (α ≈ 1.8×10⁻⁹), but this small amount is crucial for acid-base chemistry.

4. Using the Calculator

Tips: Enter the degree of dissociation (α) as a decimal between 0 (no dissociation) and 1 (complete dissociation). For water, this value is typically very small.

5. Frequently Asked Questions (FAQ)

Q1: What's the degree of dissociation for pure water at 25°C?
A: Approximately 1.8×10⁻⁹, meaning only about 0.00000018% of water molecules are dissociated.

Q2: How does temperature affect water dissociation?
A: Dissociation increases with temperature. At 100°C, α is about 5×10⁻⁸ (0.000005%).

Q3: What's the relationship between α and pH?
A: pH = -log[H⁺], where [H⁺] = α × [H₂O]. For pure water, [H₂O] ≈ 55.5 M.

Q4: Can α ever reach 1 for water?
A: No, complete dissociation would require extreme conditions not found naturally.

Q5: How is α experimentally determined?
A: Through conductivity measurements or by calculating from pH/pOH values.