Water Autoionization
H2O + H2O ⇌ H3O+ + OH−
Tổng quan
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.
Người tham gia
| Vai trò | Chất | Hệ số | Trạng thái |
|---|---|---|---|
| Chất phản ứng | Water H₂O | 2 | (l) |
Ví dụ thực tế
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.
Tầm quan trọng công nghiệp
Understanding Kw is fundamental to all aqueous chemistry, pH measurement, water quality analysis, and buffer design.
Tính chất
- Loại
- Acid-Base
- Thuận nghịch
- Có
- Năng lượng
- Thu nhiệt
- ΔH
- 55,8 kJ/mol
Phản ứng liên quan
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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)
Hydrochloric Acid and Sodium Hydroxide Neutralization
Nitric Acid and Potassium Hydroxide Neutralization
Hydrochloric Acid and Barium 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.