2H₂O ⇌ H₃O⁺ + OH⁻
Here's why:
* Equilibrium: Water's dissociation is an equilibrium process, meaning it occurs in both directions. This is represented by the double arrows (⇌).
* Hydronium Ion (H₃O⁺): While hydrogen ions (H⁺) are often used to represent the acidity of water, in reality, they are immediately solvated by water molecules, forming hydronium ions (H₃O⁺). This is the more accurate representation.
* Hydroxide Ion (OH⁻): The other product of water dissociation is the hydroxide ion, responsible for its alkalinity.
Key Points:
* Water's dissociation is a very slight process. Only a tiny fraction of water molecules are dissociated at any given time.
* The equilibrium constant for this reaction (Kw) is 1 x 10⁻¹⁴ at 25°C. This means the product of the concentrations of H₃O⁺ and OH⁻ is always constant.
* This equation is fundamental to understanding pH and the concepts of acidity and alkalinity.
