1. What is Activity Coefficient?

The activity coefficient (γ) quantifies how much an ion's behavior deviates from ideal conditions in solution due to ionic interactions. It's a correction factor used in chemical calculations to account for non-ideal behavior.

2. How Does the Calculator Work?

The calculator uses the Debye-Hückel approximation:

Where:

• \( \gamma \) — Activity coefficient (dimensionless)
• \( z \) — Charge of the ion
• \( I \) — Ionic strength (M)

Explanation: The equation shows that activity coefficients decrease (more non-ideal behavior) with increasing ionic strength and ion charge.

3. Importance of Activity Coefficient

Details: Activity coefficients are essential for accurate equilibrium calculations, solubility predictions, and electrochemical measurements in solutions with significant ionic strength.

4. Using the Calculator

Tips: Enter ion charge (can be positive or negative) and ionic strength (must be ≥0). The calculator is valid for dilute solutions (I < 0.1 M).

5. Frequently Asked Questions (FAQ)

Q1: Why does activity coefficient decrease with ionic strength?
A: As ionic strength increases, ion-ion interactions become more significant, causing greater deviation from ideal behavior.

Q2: What's the range of activity coefficients?
A: Typically between 0 and 1, though for very high ionic strengths, values slightly >1 are possible.

Q3: When is this approximation valid?
A: Best for dilute solutions (I < 0.1 M) of monovalent ions at 25°C. Extended versions exist for higher concentrations.

Q4: How does temperature affect activity coefficients?
A: The 0.51 constant is for water at 25°C. It varies slightly with temperature.

Q5: Can this be used for neutral molecules?
A: No, this form is only for charged species. Neutral molecules have different activity coefficient relationships.