Purpose
The purpose of this experiment was to look at common techniques used in gravimetric analysis by finding the amount of chloride content in an unknown salt.
Theory
The equation that is used to represent the precipitation of a chloride ion by the addition of a silver ion is as follows: . The formation of solid silver chloride is commonly used to determine the concentration of an unknown chloride. This is because silver chloride has a very low solubility, which results in very little silver chloride being redissolved into the solution, which allows all of the chloride ions to be captured, with minimal silver ions being left in excess. The solubility product (Ksp) for AgCl (s) is approximately . If pure silver chloride is the solid that is collected in this experiment, then the percentage of chloride ions in the unknown sample provided can be determined. In this experiment, the precipitation is washed in an acid media, and the reason for this is because acid prevents peptization, which is the reversion back to colloidal state which would allow the precipitate to be washed through the filter. The precipitate is also heated to coagulate. From its initial semi-solid/liquid state, the heat absorbs the liquid, transforming the precipitate into a solid state. Throughout the experiment, errors are able to affect the final outcome of the purity or total yield of product. There are many factors that can affect your overall experimental outcome, and different factors cause different results. For example, the rapid precipitation of a liquid can cause the capture of unwanted ions in your final solid substance. The mass of the final product can also be altered if the co-precipitate interferes with the amount of chloride ions that are captured. There is also a possibility of low recovery of chloride ions because of the photodecomposition properties of silver chloride. Photodecomposition means that a substance is able to decompose in the presence of light. Liquid...