Question: which two ions are present in pure water?
Answer: The ionic product, Kw pH. Variation in Kw with temperature and pressure. Weak acids. ...  H2O H+ + OH- ...  H2O (liq) H+(aq) + OH- (aq) 2 H2O(aq) H3O+(aq) + OH-(aq) ...  2 H2O(aq) H3O+(aq) + OH-(aq) ΔV = -22.3 cm3 mol-1