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Ion Product

Q = [products]/[reactants]
Quick Reference
Formula / NotationQ = [products]/[reactants]
Also Known AsReaction quotient Q, ionic product, Qsp, Kw (ion product of water)

What is Ion Product?

The ion product (Q) is the reaction quotient applied specifically to ionic reactions, calculated from the actual concentrations of ions at any given moment (not necessarily at equilibrium). For water, the ion product Kw = [H⁺][OH⁻] = 1.0 × 10⁻¹⁴ at 25°C. For sparingly soluble salts, the ion product Qsp is compared to Ksp to determine if precipitation will occur.

Formula & Notation

Q = [products]/[reactants]

Other Names / Synonyms: Reaction quotient Q, ionic product, Qsp, Kw (ion product of water)

Properties & Characteristics

Ion product Q = product of ion concentrations (with stoichiometric exponents). For water: Kw = [H⁺][OH⁻] = 10⁻¹⁴ at 25°C. For salt MA: Q = [M⁺][A⁻]. If Q < Ksp: unsaturated, no precipitation. If Q = Ksp: saturated, at equilibrium. If Q > Ksp: supersaturated, precipitation occurs. pH scale based on Kw.

Uses & Applications

Calculating whether precipitation will occur when mixing solutions. Predicting water chemistry. pH calculations. Determining if solutions are saturated. Water treatment chemistry. Analytical chemistry (fractional precipitation). Understanding acid-base equilibria (Kw basis for pH).

Safety Information

Conceptual calculation tool — no direct safety concerns. Applications (precipitation, pH adjustment) may involve corrosive acids, bases, or toxic salt solutions.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Ion Product
Formula Q = [products]/[reactants]
Synonyms Reaction quotient Q, ionic product, Qsp, Kw (ion product of water)

Frequently Asked Questions

The ion product (Q) is the reaction quotient applied specifically to ionic reactions, calculated from the actual concentrations of ions at any given moment (not necessarily at equilibrium). For water, the ion product Kw = [H⁺][OH⁻] = 1.0 × 10⁻¹⁴ at 25°C. For sparingly soluble salts, the ion product Qsp is compared to Ksp to determine if precipitation will occur.

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