Quiz2 Flashcards
In spectrophotometry we can apply Beer’s law to quantify an analyte in solution only if its concentration (or that of its colored complex) is ____ , ____ light is used and if nothing else in the sample solution ____.
True/False: Any substance that is dissolved in a solvent and absorbs visible light (360-760nm) appears colored.
True
In UV-vis spectroscopy, the absorption bands of colored complexes are broad (>100nm) because different ____ and ____ energetic levels are associated with the ground electronic state and excited electronic states.
rotational
vibrational
An analyte molecule in solution which has absorbed visible light can transition from the lowest energetic excited state S1 to the ground electronic state S0 either via a ____ transition in which the energy is dissipated among neighoring ____, or it can undergo____, in which case light is emitted which has a ____ wavelength one it absorbed.
radiationless
vibrational
fluorescence
larger
Due to their small angular divergence of 0.05o, lasers can be applied to ____ material from a surface (e.g. a tooth) which can then be analyzed by an ICP-MS and reveal the ____.
ablate
elemental composition
To measure the entire UV-vis absorption spectrum of a compound (in solution) in a faction of a second we can use a ____. The latter does not have a ____ between the light source and the sample cuvette. This instrument is particularly useful when used in conjunction with liquid chromatographic (LC) separation system as it allows one to ____ baseline separated compounds (e.g. theobromine).
protodiode array SPM
monochromator
qualitatively identify
An absorption spectrum refers to a continuum spectrum of light in which certain ____, whereas an emission spectrum only contains ____.
lenda’s are missing
a few distinct lenda’s
In the experiment carried out by Kirchhoff and Bunsen, the introduction of NaCl into the flame resulted in the formation of a black band at 589 nm in the absorption spectrum. The observed black band was attributed to the formation of ____ in the flame which ___.
Na atoms
absorbed light of 589 nm
A modern flame atomic absorption spectrometer contains a hollow cathode lamp. It is advantageous to use this light source rather than a continuum light source because ____ can be achieved.
lower detection limits
One way to determine the concentration of a metal in a sample solution involves the direction of a specific laser (lenda1) toward a flame into which the sample solution is nebulized. The measurement of the intensity of light lenda2 that is emitted from the lame (and is different from lenda1) can be used to quantify the metal. This approach is called ____.
atomic fluorescence spectrophotometry
In a flame atomic absorption spectrophotometer the analyte solution is introduced into the flame by means of a ____.
pneumatic nebulizer
A 2.00-mL solution of apotransferrin was titrated with an Fe3+ solution. It required 163 uL of 1.43 mmol ferric nitrilotriacetate to reach the end point. Why does the slope of the absorbance-versus-volume graph change abruptly at the equivalence point? How many moles of Fe(III) (=ferric nitrilotriacetate) were required to reach the end point? Each apotransferrin molecule binds two ferric ions. Find the molor concentration of apotransferrin in the 2.00-mL solution.
Because there is no more binding site for Fe3+ and the remaining free Fe3+ ion interfere with absorption reading.
163uL X 1.4mmol = 2.33X10^(-7) mol
2.33X10^(-7)mol/2mol/(2X10^(-3)L)=5.825X 10^(-5)M
