Here's why:
* Water is a neutral substance. This means it has an equal concentration of hydrogen ions (H+) and hydroxide ions (OH-).
* Autoionization of Water: Water molecules can self-ionize, meaning they can donate and accept protons. This results in the formation of small amounts of H+ and OH- ions:
* H₂O + H₂O ⇌ H₃O+ + OH-
* Equilibrium: This reaction reaches an equilibrium where the concentration of H+ and OH- ions is equal. This equilibrium constant is called Kw and is approximately 1.0 x 10⁻¹⁴ at 25°C.
In summary: Pure water contains both hydrogen and hydroxide ions in equal concentrations, making it neutral.
