What is the pH value of pure water?

The pH scale measures the concentration of hydrogen ions in a solution to determine its acidity or alkalinity [t1]. Pure water is considered the standard for neutrality because it contains equal amounts of hydrogen ions (H+) and hydroxide ions (OH-) [t1][t6]. At a standard temperature of 25°C (298 K), the ionic product of water (Kw) is 10^-14, which results in a hydrogen ion concentration of 10^-7 mol/L [t4][t5]. Since pH is defined as the negative logarithm of the hydrogen ion concentration, pure water has a pH value of exactly 7.0 [t1][t8]. While the pH can fluctuate slightly with temperature or exposure to atmospheric carbon dioxide (which forms carbonic acid), the theoretical and standard reference point for pure, neutral water remains 7 [t2][t3].