Chem 20L Fall 2002 Report Guideline for Assignment 4 (Titrations and Indicators) The Prelab work for this assignment consists of a prelab introductory report in your notebook; an in-class quiz will be given during the first 20 minutes of each lab period. Part I of the report is done individually, data will be shared for Part II. All reports are individual efforts. (I) Pre-lab Work Study questions for Quiz 3 are available on VOH The Introductory Report material will include • The title of the experiment • A reference (i.e. complete reference of the experiment including title of the lab manual, author, edition and page number of the experiment in the manual etc.) Include any changes to the procedure that you know you will make. (You will not use the indicator Nile Blue A) • A short introduction (Summarize in a two or three sentences the goals of the experiment. Outline the kinds of techniques that you will use in the experiment) • A brief flow chart summary of the key procedures of the experiment (see #2 on page 51 of lab manual) • MSDS information for 0.10 M H2SO4 and Tris(hydroxymethyl)aminomethane. Record in your notebook the product name, and common names, chemical formula, formula weight, any melting point, boiling point or density data available, health hazard data (summarize in your own words), and spill and disposal procedures (summarize in your own words). • Two data tables (see #3 and #4 in the prelab assignment on page 59) (II) Post-lab Work The Post-lab Report will include Data: In this section your report should include • An orderly record of data in tabular form with informative titles and labels Data Analysis: This section will be a series of calculations. Your report should have enough description of the calculations that someone familiar with chemistry but not the experiment of the lab manual could follow your analysis. • Calculate and explain - the normal concentration (normality, N) of the unknown acid determined with the bromocresol green indicator for each of your trials - the average normality of the unknown acid - the relative average deviation (RAD) for the unknown acid concentration - the inherent error (or relative error) in the unknown acid concentration Discussion and Conclusions: • Compare the inherent error with the RAD. Which is larger? What does this mean in terms of the precision and reproducibility of your data? What can you conclude?• Calculate the unknown acid concentration that would be determined in each titration if the end point of the indicator is assumed to be the equivalence point of the titration. • The bromocresol indicator end point corresponds to the equivalence point of this titration of sulfuric acid and base. What can you conclude about the pH of the equivalence point. Write equations to show the nature of the species in solution at the equivalence
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