Water Autoionization

H2O + H2O ⇌ H3O+ + OH−

अवलोकन

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.

प्रतिभागी

भूमिका पदार्थ गुणांक अवस्था
अभिकारक Water H₂O 2 (l)

रोजमर्रा का उदाहरण

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.

औद्योगिक महत्व

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

गुण

प्रकार
Acid-Base
प्रतिवर्ती
हाँ
ऊर्जा
ऊष्माशोषी
ΔH
55.8 kJ/mol

संबंधित अभिक्रियाएँ

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.