[AhmedEzatAlzawalaty]

i know that acid can be assayed or determined by pH determination so that we say it has a pH value of ex. 3 . or it can be titrated against a base, then we define the amount of base that neutralizes the acid and we know the end point too.But i cant convert titration to pH or clearly, i dont see any relationship betwen the two methods yet they determine the same thing> How can i understand this? i mean if you say (i am tall) and i say (i am fat)  when some one asked me and you ( how big are you?) do you get it? fat and tall are not the same measure but they both measure us and they cant be converted to one another.

[Borek]

Look up definition of pH - it is related to concentration of H⁺. In the case of strong acid concentration of H⁺ is identical to concentration of acid (strong acid is 100% dissociated). In the case of weak acid situation is more complicated (see calculation of pH of weak acid), but there is a still a relation between pH and acid concentration Thus you may use pH to calculate acid concentration.