Qualitative Analysis essays

Qualitative Analysis essays Qualitative analysis is used in the determination of the identity of a substance. It is different from quantitative analysis, which deals with the determination of the amount of a substance. In this experiment, qualitative analysis techniques are used to determine whether or not a sample contains a certain ion. When using this method, an unknown and a reactant are mixed. The result of the reaction leads to a conclusion about the presence or absence of certain ions in the unknown. Many ions react in similar ways, and although the addition of one reagent to an unknown may not identify the ion, it limits the possibilities as to what the ion could be. A sequence of reactions used to analyze a sample is called a scheme, and it usually requires a large number of reagents and separation steps. For this experiment, the unknown may contain anywhere from 2 to all of the following cations and anions: The following reagents are used to identify the ions: .1M Ba(NO3)2 (labeled as .1M Ba2+) The first four are used to identify the cations, and the last two, used in conjunction with the first four, are used to identify the anions. The identification of the ions is mainly based on solubilities. This means that something must be known about the solubility characteristics of the different ions in the presence of the available reagents. The point of the first part of the experiment is to learn which reagents cause the ions to form precipitates, and which reagents dissolve the precipitates formed by the ions. This information is used to make the flow charts for the identification on the unknown ions. For example, it is important to know that a certain reagent will dissolve the precipitate formed by one ion, while it will not dissolve the precipitate formed by another ion. This can be used to distinguish between two different precipitates present in a solution, or to confirm which ion formed the precipitate and therefore was pr...