Experiment 17

1.	Safety
2.	Objectives/Overview
3.	Procedures
4.	Observations
5.	Equipment
6.	View Techniques
7.	Waste Disposal/Clean-up
8.	Conclusions
9.	Calculations/Set-Ups
10.	Grading Scale
11.	Review Prelab Questions
12.	Review Postlab Questions

Experiment 17
Titration of a Diprotic Acid: Identifying an Unknown

PRE LABORATORY QUESTIONS

References: Brown, Lemay, and Bursten, Chemistry the Central Science, 8th ed. (2000),

pp. 133-136 (acid-base titrations);
pp. 613-615 (polyprotic acids);
pp. 650-659 (acid-base tirations, titration curves,equivalence point, polyprotic acid titrations.

Learning Center: answers to pre- and post-lab questions.

Pre-laboratory Questions

1. Define what is meant by the term "equivalence point."

2. How many equivalence points would be found for the following three acids?

_____ HC₂H₃O₂
_____ H₂C₂O₄
_____ H₃PO₄

3. A student used 0.153 M NaOH to titrate a 50.00 mL sample of 0.127 M H₃PO₄.
Calculate the volume of NaOH required for the titration.

4. A solution has an [H⁺] of 7.7 X 10-5 M.

Calculate the pH of the solution. __________
Calculate the pOH of the solution. __________

5. A 0.125 g sample of an unknown diprotic acid was titrated to its second equivalence point using 17.68 mL of 0.1179 M NaOH. Calculate the experimental molar mass of the unknown acid.