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Ionic Strength for up to Ten Species

Sum concentration-weighted squared charge numbers for up to ten dissolved ionic species.

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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

Equal 0.1 mol/L concentrations of +1 and −1 ions give ionic strength 0.1 mol/L.

I = one half × sum(c_i z_i²)

Worked example

Enter these known values and leave the other values blank.

Number of ions
2
Ionic concentration of 1st ion
.1 mol/L or mol/kg
Charge number of 1st ion
1
Ionic concentration of 2nd ion
.1 mol/L or mol/kg
Charge number of 2nd ion
-1
Ionic strength
0.1 mol/L or mol/kg

Assumptions and limitations

  • Use a common concentration basis for all ions and retain the charge sign in inputs; the square makes both signs contribute positively. The result uses the same concentration unit as the inputs.
  • The formula does not enforce electroneutrality or independently supply ion speciation. Select the number of species actually included; excluded controls do not represent a missing counter-ion.

Common questions

What does this model assume?

Use a common concentration basis for all ions and retain the charge sign in inputs; the square makes both signs contribute positively. The result uses the same concentration unit as the inputs.

Can I solve backward?

Clear the unknown value and enter compatible known values. Choices, one-way outputs and singular boundary cases cannot always be inverted.

References

Explicit physical and mathematical model domains: finite positive denominators, dilute limiting-law applicability, integral ionic charge numbers, nonnegative concentrations and normalized isotope abundances.

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