Standardizing a Solution of Sodium Hydroxide It is often necessary to test a solution of unknown concentration with a solution of a known, precise concentration. The process of concentration is called determining the unknown’s standardization. Solutions of sodium hydroxide are virtually impossible to prepare to a precise molar concentration because the substance is hygroscopic. In fact, solid NaOH absorbs so much moisture from the air that a measured sample of the compound is never 100% NaOH. On the other hand, the acid salt potassium hydrogen phthalate, KHC8H4O4, can be measured out in precise mass amounts. It reacts with NaOH in a simple 1:1 stoichiometric ratio, thus making it an ideal substance to use to standardize a solution of NaOH. OBJECTIVES In this experiment, you will Prepare an aqueous solution of sodium hydroxide to a target molar concentration. Determine the concentration of your NaOH solution by titrating it with a solution of potassium hydrogen phthalate, abbreviated KHP, with an exact molar concentration. Figure 1 MATERIALS Vernier computer interface magnetic stirrer computer stirring bar or Microstirrer Vernier pH Sensor wash bottle weighing dish or weighing paper distilled water solid potassium hydrogen phthalate ring stand 1.0 M NaOH utility clamp pipet bulb or pump 2 250 mL beakers 5 mL pipet 100 mL graduated cylinder 100 mL Volumetric flask balance (± 0.01 g) Vernier Drop Counter 100 mL beaker 60 mL reagent reservoir 10 mL graduated cylinder
Standardizing a Solution of Sodium Hydroxide It is often necessary to test a solution of unknown concentration with a solution of a known, precise concentration. The process of determining the unknown’s concentration is called standardization. Solutions of sodium hydroxide are virtually impossible to prepare to a precise molar concentration because the substance is hygroscopic. In fact, solid NaOH absorbs so much moisture from the air that a measured sample of the compound is never 100% NaOH. On the other hand, the acid salt potassium hydrogen phthalate, KHC8H4O4, can be measured out in precise mass amounts. It reacts with NaOH in a simple 1:1 stoichiometric ratio, thus making it an ideal substance to use to standardize a solution of NaOH. OBJECTIVES In this experiment, you will Prepare an aqueous solution of sodium hydroxide to a target molar concentration. Determine the concentration of your NaOH solution by titrating it with a solution of potassium hydrogen phthalate, abbreviated KHP, with an exact molar concentration. Figure 1 MATERIALS Vernier computer interface magnetic stirrer computer stirring bar or Microstirrer Vernier pH Sensor wash bottle weighing dish or weighing paper distilled water solid potassium hydrogen phthalate ring stand 1.0 M NaOH utility clamp pipet bulb or pump 2 250 mL beakers 5 mL pipet 100 mL graduated cylinder 100 mL Volumetric flask balance (± 0.01 g) Vernier Drop Counter 100 mL beaker 60 mL reagent reservoir 10 mL graduated cylinder