Experiment 15 STANDARDIZATION OF A SODIUM HYDROXIDE SOLUTION I. Learning Objectives… ±To introduce elementary acid-base reactions and their stoichiometry.±To practice quantitative precision in the laboratory. ±To standardize a solution of sodium hydroxide.II. Background Information A common method for determining the unknown concentration of a chemical in solution is the titration. In a typical titration, a solution of known concentration, the titrant, is added to (reacted with) a solution of unknown concentration in a controlled manner.A chemical reaction between the critical components of the titrant and the solution of unknown concentration is followed using one of several methods: pH dependent colorimetric indicator, pH electrode, reaction temperature, etc. The equivalence point of the reaction is determined, and the volume of titrant required to reach this equivalence pointis used to calculate the unknown solution concentration. The setup for a titration of unknown solution B (containing a colorimetric indicator, I) with titrant solution A is shown in Figure 4.1 as an example. When a colorimetric indicatoris used in a titration, a noticeable color change in the solution being titrated occurs at or near the equivalence point. Note: The term end pointrepresents the volume of titrant necessary in a titration to affect the desired indicatorcolor change. Ideally, this occurs precisely at the equivalence point,and therefore the terms "end point" and "equivalence point" are often used interchangeably. An unknown amount of an acid in a solution is determined by titration with a standard base solution (of known concentration). Additionally, an unknown amount of base in solution is measured by titration with a standard acid solution. Titrations involving acid/base neutralizationsare known as neutralizationtitrations. Other types of chemical reactions can also form the basis for titrations. Among these other reactions are those
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