water ionize 既問題

Water CANNOT be ionized in solid state (ice) and gaseous state (water vapour). Water in liquid state, no matter whether it is pure or containing solute(s), can undergo ionization. This is known as self-ionization of water.
H2O(l) ≒ H+(aq) + OH-(aq)

Each water molecule contains two O-H bonds. Because O atom has higher electronegativity than H atom, the bond pair of electrons in the O-H bond is withdrawn toward the O atom, and thus O atom carries partially negative charge (δ-) and H atom carries partially positive change (δ+). Thus, the O-H bond is polar (δ-O-Hδ+).

圖片參考：http://bioweb.wku.edu/courses/BIOL115/Wyatt/water1.gif


Therefore, by absorption of energy from surroundings, HO-H bond can be broken. The bond pair of electrons is completely occupied by the O atom, and thus OH- and H+ ions are formed. The reaction is reversibly as OH- and H+ would combine to form back water molecule. In water or solutions, most of the water molecules are not ionized.

圖片參考：http://hrsbstaff.ednet.ns.ca/dawsonrj/12%20Chem/Chapter%20notes/Chapter%2019%20%20Notes_files/image002.jpg


Since the ionization of water involves the absorption of energy from surroundings, the higher the temperature, the greater is the degree of ionization. At 25oC, both of the concentration of H+ ions and that of OH- ions in pure water are 0.0000001 M.

water always ionize...
in gas, solid, and liquid state...