Experiment 7: Acid/Base Titrations (%H2SO4) Qianyang Ding Chemistry 1A Pasadena City College V. Jaramillo, Ph.D
Introduction An acid-base titration is an analytical method of determining the concentration of an unknown acid or base solution (the analyte) by adding it to a standard reagent of known concentration (the titrant) in carefully measured amounts until the reaction reaches neutralization, which is often shown by a color change, and then calculating the unknown concentration of the acid or base. In this experiment, about 500 mL of 0.2 M NaOH solution is made and standardized by titrating it with three weighed samples of solid oxalic acid. The equation for this acid-base reaction is: H2C2O4 ⋅ 2H 2O (aq) + 2NaOH (aq) → 2H2O (l) + Na2C2O4 (aq) The standardized sodium hydroxide solution is used to analyze an unknown sulfuric acid solution. The equation to represent this acid-base reaction would be: H2SO4 (aq) + 2NaOH (aq) → Na2SO4 (aq) + 2H2O (l) The titration is done in the presence of phenolphthalein, an indicator that is colorless in acid solution but turns pink in basic solution. Two drops of phenolphthalein are sufficient for the titration.
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- Sodium hydroxide, Qianyang Ding, V. Jaramillo