EXAM #19 CHAPTER 13 MOLECULAR SPECTROSCOPY QUESTIONS AND
ANSWERS
1. What is the region studied by UV/Vis: 160-780nm
2. What is the visible light region?: 400-700 nm
3. Beer's Law: explains the relationship between absorbance, at a given wavelength and
concentration, A = bµc
4. Beer's Law terms: ebc c =
concentration
b = path length
e = extinct coefficient
5. Beer's Law Deviations: Real Deviations:
6. How do high concentrations affect beer's law?: -solvent solute interactions
-solute solute interactions
-hydrogen bonding
-affect ability of molecule to absorb light
7. How would you aim your AA?:
8. How would you measure calcium-40 and what would be a problem with ICPMS emission or
AA:
9. Beer's Law Deviations: Instrumental: problems with how absorbance measure- ments are made
limits upper level of concentration
10.Beer's Law Deviations: Chemical: related to concentration changes
acid and conjugate base forms are different colors
11.Beer's Law hold with monochromatic light but: varies with poly chromatic light
12.What is an example of instrument deviations?: using the wrong type of cell
misaligned cells
13.Types of Uncertainty: Johnson Noise Photon
Detector Shot Noise
Source Flicker
14.Photon Detector Shot Noise Equation: S(t)=K(2) * sqrt(T^2+T)
15.Describe the effect of mismatched cells:
16.Photon detector shot noise is likely to be important in: high quality UV/vis
spectrophotometers
17.What is the effect of bandwidth on detail?: the lower the bandwidth the finer the detail and
resolution between peaks
18.What is the effect of slit width on peak height?: The larger the width, the higher the peaks
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2
ANSWERS
1. What is the region studied by UV/Vis: 160-780nm
2. What is the visible light region?: 400-700 nm
3. Beer's Law: explains the relationship between absorbance, at a given wavelength and
concentration, A = bµc
4. Beer's Law terms: ebc c =
concentration
b = path length
e = extinct coefficient
5. Beer's Law Deviations: Real Deviations:
6. How do high concentrations affect beer's law?: -solvent solute interactions
-solute solute interactions
-hydrogen bonding
-affect ability of molecule to absorb light
7. How would you aim your AA?:
8. How would you measure calcium-40 and what would be a problem with ICPMS emission or
AA:
9. Beer's Law Deviations: Instrumental: problems with how absorbance measure- ments are made
limits upper level of concentration
10.Beer's Law Deviations: Chemical: related to concentration changes
acid and conjugate base forms are different colors
11.Beer's Law hold with monochromatic light but: varies with poly chromatic light
12.What is an example of instrument deviations?: using the wrong type of cell
misaligned cells
13.Types of Uncertainty: Johnson Noise Photon
Detector Shot Noise
Source Flicker
14.Photon Detector Shot Noise Equation: S(t)=K(2) * sqrt(T^2+T)
15.Describe the effect of mismatched cells:
16.Photon detector shot noise is likely to be important in: high quality UV/vis
spectrophotometers
17.What is the effect of bandwidth on detail?: the lower the bandwidth the finer the detail and
resolution between peaks
18.What is the effect of slit width on peak height?: The larger the width, the higher the peaks
1/
2
