Solubility Product Calculator

Calculate Ksp from ion concentrations, or find molar solubility from Ksp. Determine if precipitation occurs by comparing Q to Ksp for sparingly soluble salts.

💧 Equilibrium📐 Ksp = [M^m+]^m[X^x-]^x🧪 Chemistry
Cation concentration [M] (mol/L)
Cation charge / stoichiometry m
Anion concentration [X] (mol/L)
Anion stoichiometry x
Please enter valid values.

Formula & Reference

VariableSymbolFormulaUnits
Solubility Product CalculatorSee formulaKsp = [M^m+]^m[X^x-]^xmol^n/L^n

Step-by-Step Examples

Example 1
CaF2 Solubility

CaF2 dissolved: [Ca^2+]=1.30x10^-3, [F^-]=2.60x10^-3 M. m=1, x=2.

  • Ksp = [Ca^2+]^1 x [F^-]^2
  • Ksp = (1.30x10^-3)(2.60x10^-3)^2
  • Ksp = 1.30x10^-3 x 6.76x10^-6 = 8.79x10^-9
✓ Ksp(CaF2) = 8.79x10^-9
Example 2
Molar Solubility from Ksp

Ag2CrO4 Ksp=1.12x10^-12. Find molar solubility s.

  • Ag2CrO4 to 2Ag+ + CrO4^2-
  • [Ag+]=2s, [CrO4^2-]=s
  • Ksp = (2s)^2(s) = 4s^3
  • s = (Ksp/4)^(1/3) = (1.12x10^-12/4)^(1/3) = 6.54x10^-5 M
✓ s(Ag2CrO4) = 6.54x10^-5 mol/L
Example 3
Precipitation Check

Mix 0.10 M CaCl2 and 0.10 M Na2SO4 equally. Ksp(CaSO4)=4.93x10^-5.

  • After mixing: [Ca^2+]=0.050, [SO4^2-]=0.050
  • Q = 0.050 x 0.050 = 2.50x10^-3
  • Q (2.50x10^-3) > Ksp (4.93x10^-5)
  • Precipitation WILL occur
✓ CaSO4 precipitates: Q > Ksp

Real-World Applications

💧
Water Treatment
Ksp controls which minerals precipitate in water treatment and determines water hardness.
🧪
Gravimetric Analysis
Precipitation reactions with very small Ksp ensure complete removal of target ions.
💊
Pharmaceutical
Drug solubility often limited by Ksp of salt forms; affects bioavailability.
🌊
Ocean Chemistry
CaCO3 Ksp controls coral formation and dissolution in changing ocean pH.

Common Mistakes to Avoid

⚠️
Stoichiometry in Ksp

For Ag2CrO4: Ksp = [Ag+]^2[CrO4^2-]. If s = molar solubility, [Ag+]=2s, [CrO4^2-]=s. Ksp=4s^3.

⚠️
Pure solids not in expression

Ksp = [ions] only. Do not include the solid salt concentration in the expression.

⚠️
Q vs Ksp for precipitation

If Q > Ksp: precipitate forms. If Q < Ksp: solid dissolves. If Q = Ksp: saturated solution at equilibrium.

Frequently Asked Questions

What is Ksp? ▾
Solubility product constant: Ksp = [cation]^m x [anion]^x for MmXx dissolved. Applies only to sparingly soluble salts.
How do I find molar solubility s from Ksp? ▾
Set up ICE table. For MX: Ksp=s^2. For MX2: Ksp=4s^3. For M2X: Ksp=4s^3. For M2X3: Ksp=108s^5.
What is common ion effect? ▾
Adding an ion already in the Ksp expression decreases solubility. Adding NaCl to AgCl solution decreases [Ag+] solubility.
How does pH affect Ksp? ▾
For salts with basic anions (CaCO3, Fe(OH)3), lower pH dissolves the salt. Ksp of hydroxides decreases with increasing pH.
What are typical Ksp values? ▾
AgCl: 1.8x10^-10 (very insoluble). BaSO4: 1.1x10^-10. CaCO3: 3.3x10^-9. CaF2: 3.9x10^-11. Fe(OH)3: 2.8x10^-39 (extremely insoluble).

Related Chemistry Calculators

💧 Common Ion Effect💧 Solubility Calculator⚖️ Equilibrium Constant⚖️ Reaction Quotient🔬 pH Calculator

Formula Explorer connections

Interpretation: This formula describes how reactants, products, ions or phases distribute when opposing processes reach equilibrium. Assumption: Use equilibrium rather than initial concentrations, correct stoichiometric exponents, and the specified temperature; activities may replace concentrations in nonideal systems.

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