Analysis of an Unknown Mixture by Acid-Base Titration

Analysis of an Unknown Mixture by Acid-Base Titration 

PURPOSE OF EXPERIMENT Determine the percent composition of a two-component mixture of tartaric acid and a component which is unreactive with acids and bases. 

In this experiment as in Experiment 25, you will standardize a solution of sodium hydroxide using oxalic acid dihydrate, H2C2O4 2H20, as the primary standard. This solution of base will then be used to titrate the unknown mixture. Phenolphthalein will be used as the indicator of the endpoint in all titrations. Your goal is to determine the percent composition by mass of the mixture. 

Thoroughly clean, using cleanser and buret brush if necessary, a buret, a graduated cylinder, a 500-mL Florence flask, and three 250-mL Erlenmeyer flasks so that water will drain well from them. Fill your wash bottle with distilled water to use at your desk throughout this experiment. Rinse the apparatus you have cleaned with distilled water. Do this at the sink, not at the distilled-water tap, and do not waste distilled water. 

Prepare a dilute solution of sodium hydroxide by adding about 50. mL of the stock solution of sodium hydroxide, NaOH, provided on the reagent table, to 250. mL of distilled water contained in a 500-mL Florence flask. Stopper and shake the flask to mix the solution. Keep the flask stoppered except when transferring the solution to your buret. Assume the concentration of the NaOH solution you have just prepared is 0.12 M. 

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