Chemistry coursework
Titration assignement:
Aim:
The aim of my investigation is to determine the solubility of calcium Hydroxide solution with the aid of the titration process.
Titration can be defined as the method of determining the concentration of a substance in solution by adding to it a standard reagent of known concentration in carefully measured amounts until a reaction of definite and known proportion is completed, as shown by a color change or by electrical measurement, and then calculating the unknown concentration.
An example could be, a given volume of a solution of unknown acidity may be titrated with a base of known concentration until complete has occurred. This point is called the equivalence point and is generally determined by observing a color change in an added indicator such as phenolphthalein. From the volume and concentration of added base and the volume of acid solution, the unknown concentration of the solution before titration can be determined. Titrations can also be used to determine the number of acidic or basic groups in an unknown compound. A specific weight of the compound is titrated with a known concentration of acid or base until the equivalence point has been reached. From the volume and concentration of added acid or base and the initial weight of the compound, the , and thus the number of acidic or basic groups, can be computed. Instead of adding an indicator to observe the equivalence point, one can construct a graph on which the (see separate article) at regular intervals is plotted along one axis and the number of moles of added acid or base at these intervals along the other axis; such a plot is called a titration curve and is usually sigmoid (S-shaped), with the inflection point, where the curve changes direction, corresponding to the equivalence point. From the pH at the equivalence point, the dissociation constant of the acidic or basic group can be determined (see ). If a compound contains several different acidic or basic groups, the titration curve will show several sigmoid-shaped curves like steps and the dissociation constant of each group can be obtained from the pH at its corresponding equivalence point.
