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Ionic Product of Water

[H+][OH−] = Kw = 1.0×10⁻¹⁴ at 25°C
Quick Reference
Formula / Notation[H+][OH−] = Kw = 1.0×10⁻¹⁴ at 25°C
Also Known AsIonic product of water, Kw, Autoprotolysis constant

What is Ionic Product of Water?

The equilibrium constant for the autoionization of water: Kw = [H⁺][OH⁻] = 1.0 × 10⁻¹⁴ at 25°C. This relationship links [H⁺] and [OH⁻] concentrations in any aqueous solution and is the basis for the pH scale.

Formula & Notation

[H+][OH−] = Kw = 1.0×10⁻¹⁴ at 25°C

Other Names / Synonyms: Ionic product of water, Kw, Autoprotolysis constant

Properties & Characteristics

Water undergoes autoionization: 2H₂O ⇌ H₃O⁺ + OH⁻. Kw varies with temperature: at 0°C = 1.14×10⁻¹⁵, at 25°C = 1.0×10⁻¹⁴, at 37°C = 2.4×10⁻¹⁴, at 100°C = 5.5×10⁻¹³. Neutral solution: [H⁺] = [OH⁻] = √Kw. At 37°C, neutral pH = −log(√2.4×10⁻¹⁴) ≈ 6.8. Forms the basis of the pH + pOH = pKw relationship.

Uses & Applications

Foundation of all acid-base calculations in aqueous solution. Deriving Henderson-Hasselbalch equation. Calculating pH of salt solutions. Understanding physiological pH (body temperature shifts neutral pH). Corrosion calculations. Water treatment chemistry.

Safety Information

Theoretical constant. Understanding Kw is essential for correctly calculating acidic or basic concentrations, preventing errors in solution preparation that could create dangerously corrosive solutions.

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

Key Facts

Term Ionic Product of Water
Formula [H+][OH−] = Kw = 1.0×10⁻¹⁴ at 25°C
Synonyms Ionic product of water, Kw, Autoprotolysis constant

Frequently Asked Questions

The equilibrium constant for the autoionization of water: Kw = [H⁺][OH⁻] = 1.0 × 10⁻¹⁴ at 25°C. This relationship links [H⁺] and [OH⁻] concentrations in any aqueous solution and is the basis for the pH scale.

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