Water Autoionization

H2O + H2O ⇌ H3O+ + OH−

개요

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.

참여 물질

역할 물질 계수 상태
반응물 Water H₂O 2 (l)

일상 속 예시

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.

산업적 중요성

Kw 이해는 모든 수성 화학, pH 측정, 수질 분석, 완충액 설계의 기본입니다.

성질

유형
Acid-Base
가역 반응
예
에너지
흡열
ΔH
55.8 kJ/mol

관련 반응

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.