Enter your salt's cation coefficient (x), anion coefficient (y), and either a Ksp value or molar solubility — optionally add common ion concentrations — and the Ksp Calculator returns the primary result alongside equilibrium concentrations and solubility in g/L.
Primary Result
--
Equilibrium Cation Concentration
--
Equilibrium Anion Concentration
--
Solubility (g/L)
--
A Ksp calculator computes the solubility product constant or molar solubility for sparingly soluble ionic compounds. It uses the equilibrium expression Ksp = [A]^x[B]^y for a salt AxBy to determine how much of the compound dissolves in water at equilibrium.
Enter the coefficients from your balanced dissolution equation. For example, CaF₂ → Ca²⁺ + 2F⁻ has x=1 (cation coefficient) and y=2 (anion coefficient). These coefficients are crucial for the correct Ksp expression.
Common ions are ions already present in solution before the salt dissolves. They reduce the solubility of the salt due to Le Chatelier's principle. Enter their initial concentrations in the common ion fields to account for this effect.
Use mol/L for molar solubility and concentrations. Ksp values are typically very small numbers (like 1.8×10⁻¹⁰) and are unitless, though technically they have units of (mol/L)^(sum of coefficients).
Ksp calculations assume ideal behavior and that activities equal concentrations. Real solutions may deviate due to ionic strength, temperature effects, and complex ion formation. Results are most accurate for dilute solutions at 25°C.
While this calculator focuses on equilibrium calculations, you can compare calculated ion concentrations with known Ksp values to predict precipitation. If the ion product Q exceeds Ksp, precipitation should occur.
Common examples include AgCl (Ksp = 1.8×10⁻¹⁰), CaF₂ (Ksp = 3.9×10⁻¹¹), and PbCl₂ (Ksp = 1.6×10⁻⁵). These values are temperature-dependent and found in chemistry reference tables.
Ksp values are temperature-dependent. For most salts, Ksp increases with temperature, meaning higher temperature increases solubility. However, some compounds like calcium sulfate show the opposite trend.