Prelab Assignment
Prelab Assignment
As part of your individual preparation for lab, read the experiment and answer the following questions in your lab notebook. The copy of your answers on the duplicate (yellow) pages is due at the beginning of the lab period. You must attend recitation to receive credit for this assignment. You must show your work and label units to get full credit on calculations.
- Describe, in your own words, the general purpose of using a blank solution when performing spectroscopic analysis. How will you prepare the blank for this experiment? (In other words, what solutions will you combine to make the blank?)
- Calculate the concentration of Fe2+ in each of the standard solutions you will prepare in lab. Refer to the table on p. 77 of your lab manual. Show your work.
- How will you prepare the unknown sample for spectroscopic analysis in this experiment? (i.e. What solutions and volumes will you combine? What equipment will you use? What will the total volume of the sample be?) What is the dilution factor of this sample?
- Write the chemical equation for the reaction of Fe(II) ion with phenanthroline. (Use the abbreviation phen for the phenanthroline.) Indicate the color of each reactant and the product. What is the molar ratio of Fe(II) ion to the Fe(II)-phenanthroline complex ion?
- Use Excel (or other graphing software) and the data below to make a calibration plot and use it to calculate the concentration of iron(III) ion in the unknown solution. The cell path length was 1.00 cm in all cases and the wavelength used in the determination was 470 nm. You must include a printed graph with the equation of the line shown with your prelab. Refer to Chapter 1 in the lab manual for instructions on using Excel to create a chart.
Concentration of Fe3+ (M) | Absorbance |
2.67 x 10–6 | 0.019 |
5.33 x 10–6 | 0.051 |
1.33 x 10–5 | 0.159 |
2.67 x 10–5 | 0.290 |
4.00 x 10–5 | 0.472 |
Unknown | 0.328 |
6. In your laboratory notebook, record the experimental procedure you will follow in lab. The procedure is your experimental plan and can be organized as an outline, a flowchart, or a numbered list of steps. Design your procedure so that you can perform the experiment with minimal reference to your lab manual.
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