Volumetric Analysis I
Standardization of NaOH Solution
After completing this experiment, the student should be able to: 1.
Demonstrate the concept of quantitative analysis.
Make solution and standardize it.
Explain the difference between primary and secondary standard solutions. Quantitatively determine the concentration of a base.
Titration is a common method of quantitative analysis used to determine the concentration of an unknown substance in a solution. The method is easy to use if the quantitative relationship between two reacting solutions is known. It is particularly well-suited to acid-base and oxidation-reduction reactions. In this course, we will analyze commercial products such as household vinegar and bleach.
In the case of acid-base titrations, these permit the determination of concentrations of unknown acids or bases with a high degree of accuracy. In order to analyze unknown acids or bases, we must have a “standard solution” to react with the unknowns. A standard solution is one in which the concentration is accurately known. We will first prepare a standard solution of NaOH. One way to prepare a standard solution is to dissolve an accurately massed amount of the substance and dilute it to a measured volume. In this way, the concentration can be calculated exactly. However, it is usually impossible to obtain NaOH of sufficient purity to use it as a primary standard. Moreover, NaOH is highly hygroscopic, therefore absorbs water during the weighing process. An indirect method is more practical for obtaining a standard solution of NaOH. We will prepare a solution of NaOH of approximate molarity and standardize it against a primary standard of known purity. A primary standard is a substance that should:
* be of high purity
* remain unchanged in air during massing and remain stable during storage * have a high molar mass to reduce massing errors
* react with the solution to be...
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