define acid and base and explain the concept of ph
pH 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.[1] 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.[2]
Equivalence point The equivalence point, or stoichiometric point, of a chemical reaction is the point at which chemically equivalent quantities of bases and acids have been mixed. In other words, the moles of acid are equivalent to the moles of base, according to the equation (this does not necessarily imply a 1:1 molar ratio of acid:base, merely that the ratio is the same as in the equation). It can be found by means of an indicator, for example phenolphthalein or methyl orange.