* Self-ionization of water: Water molecules (H₂O) can spontaneously react with each other, forming a hydronium ion (H₃O⁺) and a hydroxide ion (OH⁻).
* H₂O + H₂O ⇌ H₃O⁺ + OH⁻
* Equilibrium: This reaction reaches equilibrium, meaning the rate of forward and reverse reactions are equal. At equilibrium, the concentrations of hydronium ions and hydroxide ions are equal.
* pH and pOH:
* pH is a measure of the concentration of hydronium ions (H₃O⁺).
* pOH is a measure of the concentration of hydroxide ions (OH⁻).
* Neutral pH: When the concentrations of H₃O⁺ and OH⁻ are equal, the pH and pOH are also equal. Since the pH scale is logarithmic, a pH of 7 represents a neutral solution, where the concentrations of H₃O⁺ and OH⁻ are both 10⁻⁷ moles per liter.
Therefore, the equal concentration of hydrogen (H⁺) and hydroxide (OH⁻) ions in pure water, due to self-ionization, leads to its neutral pH of 7.
