Prelab Questions
1)To standardize a solution of approximately 0.1 M NaOH, a student dissolved a known mass of KHP(potassium hydrogen phthalate, KHC8H4O4, MW 204.2 g/mol) in water, and titrated it with the NaOH whose molarity was only approximately known. The KHP solution was made by dissolving 0.3972g in water. It took 18.56ml of the NaOH solution to titrate the KHP solution to a phenolphthalein end point
Molarity of the NaOH solution (4 s.f) = ___________

2)A total of17.58mL of 0.0984M NaOH was required to reach a phenolphthalein end point when titrating a 2.15mL sample of vinegar. Calculate the molarity of acetic acid present in the sample.
Molarity of acetic acid = ____________

3)A total of 14.98mL of 0.1062M NaOH was required to reach phenolphthalein end point when titrating a 5.01mL sample of fruit juice. Assuming that the only acid present in the juice is citric acid (a triprotic acid), calculate the molarity of citric acid in the juice sample.
Molarity of citric acid= ____________

4)Fred E. Student, an impatient youth, did not follow the directions in the write-up:“Note in Fig.5, Good Technique, 1 or 2 fingers are behind the stopcock, bracing it. The thumb and fingertips give sensitive flow control, and the Erlenmeyerflaskis held and swirled during the titration. In Fig. 6, Poor Technique, the hand is off to one side, the Erlenmeyer is not swirled, and the titrant is introduced in bursts, not dropwise”Using this poor technique, Fred blew past the endpoint, getting a dark pink solution.He wrote down the volume of NaOH dispensed from the buret anyway, and used this volume to calculate the concentration of the acid he was titrating.What effect would this have on the reported acid concentrations (too high or too low)?

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