How to Calculate the Ionic Strength of a Solution?

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The ionic strength of a solution is a calculated using the concentration of dissolved substances in a solution along with the valence of the species in question. Ionic strength represents the relative interactions of ions with water molecules and other ions in a solution.

The formula is given (where “I” is the variable for ionic strength):

I = 1 /2 ∗ ∑ci ∗ zi2

The variables are:

  • “I” is ionic strength
  • ci is the concentration of the “i” species, mole/L
  • zi2 is the valence (or oxidation) number of the “i” species

Measurement of ionic strength is important in chemistry. Since ionic strength relates to the activity of ions, In order for the results of experiments to be comparable, solutions of comparable ionic strength are used.