The pH scale is a measure of how acidic or basic a solution is. The range of the pH scale is from 0 to 14, with 7 being neutral. A pH of less than 7 indicates acidity, while a pH greater than 7 indicates basicity or alkalinity. The pH scale is logarithmic, meaning that a change of 1 pH unit corresponds to a ten-fold change in hydrogen ion concentration/Acids_and_Bases/Acids_and_Bases_in_Aqueous_Solutions/The_pH_Scale). The pH range for the existing solution will always lie in the range between 0 and 14. However, in exceptional cases, the pH of a strong acid solution could be less than zero, and in highly concentrated basic solutions, the pH could be more than 14.