Ionic Strength Calculator Formula
Understand the math behind the ionic strength calculator. Each variable explained with a worked example.
Formulas Used
Ionic Strength
ionic_strength = 0.5 * (conc_1 * pow(charge_1, 2) + conc_2 * pow(charge_2, 2))Variables
| Variable | Description | Default |
|---|---|---|
conc_1 | Concentration of Ion 1(M) | 0.1 |
charge_1 | Charge of Ion 1 | 2 |
conc_2 | Concentration of Ion 2(M) | 0.2 |
charge_2 | Charge of Ion 2 | 1 |
How It Works
How to Calculate Ionic Strength
Formula
I = 0.5 × Sum(c_i × z_i^2)
Ionic strength measures total charge concentration and affects activity coefficients.
Worked Example
0.1 M CaCl2: 0.1 M Ca2+ and 0.2 M Cl-.
conc_1 = 0.1charge_1 = 2conc_2 = 0.2charge_2 = 1
- 01I = 0.5 × (0.1 × 4 + 0.2 × 1)
- 02I = 0.5 × (0.4 + 0.2)
- 03I = 0.3 M
Frequently Asked Questions
What is ionic strength?
A measure of total ion concentration weighted by charge squared, used in Debye-Huckel calculations.
Why square the charges?
Highly charged ions have a disproportionately larger effect on the electrostatic environment.
How does ionic strength affect solubility?
Higher ionic strength generally increases solubility of sparingly soluble salts via the salt effect.
Ready to run the numbers?
Open Ionic Strength Calculator