Is Water an Acid?
Water is neither acidic nor basic; it's neutral. However, it possesses the unique ability to act as both an acid and a base, a property known as being amphiprotic.
The neutrality of pure water stems from its self-ionization: H₂O + H₂O ⇌ H₃O⁺ + OH⁻. This means water molecules can donate (act as an acid) and accept (act as a base) protons (H⁺). At 25°C, the concentration of hydronium ions (H₃O⁺) and hydroxide ions (OH⁻) are equal, resulting in a pH of 7, which is neutral.
Several sources confirm this:
- Chemistry LibreTexts: "In this reaction, the water molecule donates a proton to the NO2− ion, making OH−(aq). As the proton donor, H2O acts as a Brønsted-Lowry acid..." This highlights water's ability to donate a proton, acting as an acid. https://chem.libretexts.org/Bookshelves/Introductory_Chemistry/Basics_of_General_Organic_and_BiologicalChemistry(Ball_et_al.)/10%3A_Acids_and_Bases/10.03%3AWater-_Both_an_Acid_and_a_Base
- Study.com: "Water is both an acid and a base. This makes water an amphiprotic compound. Water acts as an acid and base with other molecules..." https://study.com/learn/lesson/properties-water-acid-base.html
- Reddit (r/AskChemistry): "...water is an acid/base because it is able to both accept and donate a proton." https://www.reddit.com/r/AskChemistry/comments/1bhd3ua/is_water_really_an_acidbase_or_is_it_the_ions/
While water can act as both an acid and a base, its overall pH remains neutral under standard conditions. The acidity or basicity of a solution is determined by the relative concentration of hydronium and hydroxide ions.
