Water Autoionization

H2O + H2O ⇌ H3O+ + OH−

نظرة عامة

Water undergoes autoionization where one molecule acts as an acid (donates H⁺) and another acts as a base (accepts H⁺). The equilibrium constant Kw = [H₃O⁺][OH⁻] = 1.0 × 10⁻¹⁴ at 25 C, defining pH 7 as neutral. This endothermic reaction shifts right at higher temperatures, decreasing neutral pH.

المشاركون

الدور المادة المعامل الحالة
متفاعل Water H₂O 2 (l)

مثال من الحياة اليومية

The pH scale itself is defined by water autoionization, which is why pH 7 is neutral at 25 C and why neutral pH changes at different temperatures.

الأهمية الصناعية

Understanding Kw is fundamental to all aqueous chemistry, pH measurement, water quality analysis, and buffer design.

الخصائص

النوع
Acid-Base
قابل للعكس
نعم
الطاقة
ماص للحرارة
ΔH
55,8 kJ/mol

التفاعلات ذات الصلة

Hydrochloric Acid and Barium Hydroxide Acetic Acid and Sodium Acetate Buffer System Acetic Acid Dissociation in Water Ammonia and Hydrochloric Acid Ascorbic Acid and Sodium Hydroxide Barium Hydroxide and Ammonium Thiocyanate (Endothermic) Carbonic Acid and Sodium Hydroxide Aluminum Hydroxide as Amphoteric Acid with NaOH Aluminum Chloride and Chloride Ion (Lewis Acid-Base) Formic Acid and Sodium Hydroxide

Frequently Asked Questions

What is the equation for Water Autoionization?
The balanced equation is: H₂O + H₂O ⇌ H₃O⁺ + OH⁻.
What type of reaction is Water Autoionization?
Water Autoionization is a acid-base reaction. It is reversible under certain conditions.
Is Water Autoionization exothermic or endothermic?
Water Autoionization is endothermic (absorbs energy). The enthalpy change (ΔH) is 55.8 kJ/mol.