Enter your solution's ions — set the number of ions, then fill in each ion's concentration and charge — and this Ionic Strength Calculator computes the overall ionic strength of your solution along with the individual ion contributions so you can see exactly how much each species is pulling its weight.
Ionic Strength
--
Total Ion Contributions
--
Ionic strength is a measure of the concentration of dissolved ions in a solution. It quantifies the electrical environment created by all ions present and affects chemical equilibria, reaction rates, and protein interactions.
Ionic strength is calculated using the formula I = ½Σ(ci·zi²), where ci is the molar concentration of ion i and zi is its charge. Sum this calculation for all ions in the solution and multiply by 0.5.
Ionic strength is important for understanding electrostatic interactions in solutions, predicting salt solubility, designing buffer systems, and studying protein behavior. It's crucial in analytical chemistry and biochemical research.
For buffers, consider all ionic species present including the buffer components and any added salts. Remember that buffer ionic strength varies with pH as the equilibrium between acid and base forms changes.
For ZnCl₂: I = ½[(1.2 × 2²) + (2.4 × 1²)] = ½[4.8 + 2.4] = 3.6 mol/L. Note that Zn²⁺ has charge +2 and each Cl⁻ has charge -1.
If given molarity of a compound, first determine the ion concentrations after dissociation. For example, 0.1 M NaCl gives 0.1 M Na⁺ and 0.1 M Cl⁻. Then apply the ionic strength formula.
For KCl, both K⁺ and Cl⁻ have charge ±1. If the concentration is C mol/L, then I = ½[(C × 1²) + (C × 1²)] = C mol/L. The ionic strength equals the molar concentration for 1:1 electrolytes.