Use this chemistry calculator to reproduce a named relationship with explicit quantities and units for study, laboratory planning, or an independent numerical check.

Ion 1 conc

Required number input.

Ion 1 charge

Required integer input.

Ion 2 conc

Required number input.

Ion 2 charge

Required integer input.

Compute ionic strength I = 0.5 * sum(ci * zi^2) for two ion species. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Ionic strength

The resulting ionic strength returned as a number.

• The result is conditional on the stated model, constants, standard state, temperature, pressure, composition, and unit basis. Real mixtures and measurements can depart from ideal behavior and carry uncertainty not represented by a single calculated value.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Check units and significant figures, compare the result with limiting cases, and use measured or source-specific constants where available. Laboratory, safety, and regulatory decisions require validated methods and appropriate uncertainty analysis.

• Debye-Huckel Limiting Law

  Compute an ion activity coefficient in water at 25 °C with the Debye-Hückel limiting law, intended for ionic strength up to 0.01 mol/L.

• Charge Balance Checker

  Sum signed ionic charges and check electroneutrality of a species or solution.

• Gibbs Surface Excess

  Estimate surface excess Γ from the slope dγ/dln(activity) using Γ=−slope/(nRT). Supply the appropriate ionic/species factor n; the ideal-activity approximation and chosen slope determine the result.