There are many different ways in which the concentration of a solution can be reported, but concentration units always describe the ratio of the amount of solute in a sample to the amount of either the solvent or the solution. Because so many calculations are based on the concept of the mole, the most commonly used concentration unit is based on the number of moles of solute per liter of solution. Starting with a known volume of a solution of known molarity, we should be able to prepare a more dilute solution of any desired concentration. Click here to check your answer to Practice Problem 15 Click here to see a solution to Practice Problem 15 Titration We can measure the concentration of a solution by a technique known as a titration . The solution being studied is slowly added to a known quantity of a reagent with which it reacts until we observe something that tells us that exactly equivalent numbers of moles of the reagents are present.
Titrations are therefore dependent on the existence of a class of compounds known as indicators .
The endpoint of an acid-base titration is the point at which the indicator turns color. The equivalence point is the point at which exactly enough base has been added to neutralize the acid.