Solutions

How do you calculate ionic strength and activity?

I = ½ Σ cz², plus activity coefficients (Debye-Huckel to Davies). The relationship used is I = ½ Σ cᵢzᵢ².

Open the Ionic strength and activity calculator

Worked example

Every number below is computed by the calculator, not typed in

What you are given

  • Ions: [{"ion":"Na+","conc":"100","z":""},{"ion":"Cl-","conc":"100","z":""}]

Formula: I = ½ Σ cᵢzᵢ²

Do it with your own numbers.

The Ionic strength and activity calculator is free, shows every step, flags the hazards, and works offline once loaded. No account, no signup.

Open the calculator
Related calculators
Make a solution
Weigh a solid or pipette a liquid: enter what you have, get the bench step.
The Fixer (rescue a weigh-out)
Weighed the wrong amount? Get the volume to dissolve it in to hit your target.
Hydrate mass adjuster
Protocol assumes one hydrate, you have another? Get the corrected mass.
Molarity to normality
N = M × n, with the equivalence factor you confirm for the reaction.
Simple dilution
C₁V₁ = C₂V₂, exactly how much stock and diluent to mix.
Serial dilution
A fold-dilution series, tube by tube.
All 57 calculators
Browse the full catalog by category.