4.

a. State Beer’s Law. What is meant by the statement that Beer’sLaw is a limiting law?

b. Describe two apparent deviations from Beer’s Law and indicatehow the deviation specifically affects the calibration curve.

c. Phosphate ions do not absorb radiation in the visible regionof the electromagnetic spectrum. Nonetheless, Phosphate ions can bedetected quantitatively utilizing absorption spectrophotometry inthe visible region. Explain.

d. Why can’t an ultraviolet spectrophotometer be used to obtaininfrared spectra? Be specific.

e. State three factors that contribute to photometric error.

f. Why is fluorescence spectroscopy more sensitive thanabsorbance spectroscopy?

g. Why must there be a vertical and horizontal adjustment of thehollow cathode lamp position with respect to the flame for ananalysis using atomic absorption spectroscopy?

h. Why is a narrow slit width important for qualitativeanalysis, but not as critical for quantitative analysis?

i. What is the advantage of using a double beam instrument overa single beam instrument?

j. The molar absorptivity of p-nitrophenol at 407 nm is shown inthe table two pH’s. What does the information tell you aboutp-nitrophenol?

                       

                       pH                  molar absorptivity

                       4.0                            330

                       9.0                        18330

k. The temperature of the plasma used in ICP is about twice ashigh as the temperature of a flame, yet there are few ionizationproblems associated with the use of an ICP. Explain.

l. Use an energy diagram to illustrate the change(s) in energythat an electron undergoes when fluorescence is observed for amolecule. Explain the energy diagram.

m. An acetylene/air flame (2450 K) can be used to analyze asample containing Pd by atomic absorption spectroscopy whereas theanalysis of V requires an acetylene/nitrous oxide flame (3000K).Explain.