Take Home Exam 1 - Chem 434 -Spring 2003
1. (Chapter 1) I am trying to evaluate the a calibration curve that I obtained for a set of Atomic
Absorption experiments. Below is a data table summarizing my results:
Standard Concentration
0 ppm
1 ppm
2ppm
4ppm
8ppm
10ppm
0.596434 1.510757 2.348576 4.425284 7.975521 9.588525
Instrum ent
Readings
0.935629
1.401997
2.721855
4.396837
8.097156
9.666781
0.672325
1.699797
2.415565
4.322336
7.931395
9.72997
0.755944
1.783089
2.424035
4.503543
8.060935
9.438306
0.985663
1.85018
2.324526
4.232748
8.081333
9.265445
0.552469
1.680483
2.734043
4.594842
8.204793
9.27105
0.658404
1.731816
2.372552
4.392391
7.939006
9.477733
0.541983
1.56333
2.668554
4.43118
7.88795
9.557858
0.674696
1.466759
2.744857
4.298747
7.760275
9.663501
0.541609
1.492695
2.470552
4.350143
8.021469
9.341184
Based on this data, What is:
The analytical sensitivity for this method?
The minimum distinguishable analytical signal or this method? (Assume you need k=2)
The detection limit for this method?
The limit of quantitation for this method?
The limit of linearity for this method?
The dynamic range for this method?
2. (Chapter 6)
Calculate the energy, frequency in Hertz, frequency in cm-1 of a photon of UV radiation
with a wavelength of 200 nm.
Calculate the energy, frequency in Hertz, frequency in cm-1 of a photon of visible
radiation with a wavelength of 600 nm.
Calculate the energy, frequency in Hertz, and wavelength of a photon of visible light with
a frequency of 2000 cm-1.
3. (Chapter 7)
In some Instrumentation classes, you actually have to put an instrument together. Let’s
assume that your assignment is to build a single beam visible spectrometer, and a single beam IR
spectrometer. For each of the components below, compare and contrast the components you
would use to build these two machines. Why did you chose this particular component for your
instrument.
Source
Wavelength selector
Windows, lenses or prisms
Detector
Sample holder
4. (Chapter 8)
In problem 2 you calculated the energy of a photon of UV, visible, and IR light. This also
corresponds to the energy needed to move a molecule from a ground state to an excited state
using this radiation. In the next chapter we will start with the assumption that a molecule is
always in its ground state, and that no molecules are in the excited state. I want to see if this is
true. Use the Bolzmann equation (8-1) to determine how may molecules are already in an excited
state due to the temperature - at room temp (25oC ), in a Bunsen burner flame (1800oC) and in an
ICP flame (6000K), for each of these transitions.
5. (Chapter 9)
Let’s say you just moved in to an old house, and you want to know if the wall have lead
paint on them. You have chipped off about a 1 g sample of paint from a wall for analysis.
Describe, in as much detail as possible how you will go to the lab and analyze this sample for
lead. To help you get started I have included copies of the pages out of the Atomic Absorption
manual that describe the parameters for Pb analysis.
Things I want to see in your analysis: Which do you expect to be more sensitive
Absorption or Emission? What wavelengths and slit widths will you use and why? What
sensitivity do you expect to see at these settings? What will you use as your standard(s)? Are
there any precautions you want to use? How do you think you will prepare your sample?
This is a wide open question. Feel free to use the Web or library resources to see if you can find
a procedure you can use directly, or you think you might be able to modify, just make sure you
cite a reference for the procedure. If you are interested, I could turn this into a more of a term
paper type assignment, rather than a 1 day test question.