Students use a primary standard in order to prepare a solution of exact molar concentration.
Students employ dry benzoic acid as the primary acid standard for determining the molar concentration of a sodium hydroxide solution. First, an accurately measured mass of dry benzoic acid is dissolved in deionized water. A prepared sodium hydroxide solution is then dispensed from a burette into the benzoic acid solution containing phenolphthalein indicator until the stoichiometric point is reached. Using the balanced acid-base reaction equation, students calculate the molar ratio of sodium hydroxide in solution.