<Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> In chemistry, pH (/ piːˈeɪtʃ /) is a logarithmic scale used to specify the acidity or basicity of an aqueous solution . It is approximately the negative of the base 10 logarithm of the molar concentration, measured in units of moles per liter, of hydrogen ions . More precisely it is the negative of the base 10 logarithm of the activity of the hydrogen ion . Solutions with a pH less than 7 are acidic and solutions with a pH greater than 7 are basic . Pure water is neutral, at pH 7 (25 ° C), being neither an acid nor a base . Contrary to popular belief, the pH value can be less than 0 or greater than 14 for very strong acids and bases respectively . </P> <P> Measurements of pH are important in agronomy, medicine, chemistry, water treatment, and many other applications . </P>

Where are bases found on the ph scale