The pH scale that is typically presented in textbooks ranges from zero to 14, yet a pH higher than 14 or lower than 0 is possible. How is a pH lower than 0 mathematically possible if you consider that pH = -log,o [H*]? Hint: Consider that pure water has an agreed-upon pH of 7. At a pH of 7, the concentration of OH and H* are equal; each has a concentration of 10-7 moles/liter.