1. What is Ionic Strength?

Ionic strength (I) is a measure of the concentration of ions in solution that accounts for both their concentrations and charges. It's calculated using the formula:

where c_i is the molar concentration of each ion and z_i is its charge number.

2. How Does the Calculator Work?

The calculator uses the ionic strength equation:

Where:

• \( c_i \) — Molar concentration of ion i (mol/L)
• \( z_i \) — Charge number of ion i (dimensionless)
• The sum is taken over all ions in solution

Explanation: The equation weights each ion's contribution by the square of its charge, making multivalent ions contribute more significantly to the ionic strength.

3. Importance of Ionic Strength

Details: Ionic strength affects activity coefficients, reaction rates, solubility, and other solution properties. It's crucial in fields like electrochemistry, biochemistry, and environmental science.

4. Using the Calculator

Tips: Enter concentrations in mol/L (one per line) and corresponding charges (one per line). The calculator will sum all contributions and multiply by 0.5 to get the ionic strength.

5. Frequently Asked Questions (FAQ)

Q1: Why is ionic strength important?
A: It determines the activity coefficients of ions in solution, affecting chemical equilibria, reaction rates, and electrochemical properties.

Q2: What are typical ionic strength values?
A: Distilled water has I ≈ 0, while seawater has I ≈ 0.7 mol/L. Physiological solutions are typically 0.15-0.2 mol/L.

Q3: How does ionic strength affect solubility?
A: Higher ionic strength generally increases solubility of non-electrolytes (salting-in) but decreases solubility of electrolytes (salting-out).

Q4: What's the Debye-Hückel equation?
A: It relates ionic strength to activity coefficients: \( \log \gamma_i = -A z_i^2 \sqrt{I} \), where γ is the activity coefficient.

Q5: Does ionic strength affect pH measurements?
A: Yes, ionic strength affects the activity of H⁺ ions, so pH measurements in high ionic strength solutions may need correction.