In atomic absorption spectroscopy, the mechanism of light absorption is
A. Selective absorption of light during molecular vibration and rotation energy level transitions
B. The absorption when the ground state atom absorbs the characteristic radiation and transitions to the excited state and then returns to the ground state
C. The absorption caused by the molecular electrons absorbing the characteristic radiation and then transitions to the excited state
D. Absorption caused by transition to excited state after ground state atom absorbs the characteristic radiation
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Indicators used in complexometric titration belong to ( )
A. adsorption indicator
B. acid-base indicator
C. proprietary indicators
D. metal indicators
The detectors commonly used in atomic absorption spectrophotometers are:
A. Photocell
B. phototube
C. photomultiplier tube
D. photosensitive plate
In the theory of atomic absorption analysis, one of the basic conditions for substituting peak absorption for integrated absorption is:
A. The half width of the emission line of the light source is much smaller than the half width of the absorption line
B. The half width of the emission line of the light source should be equivalent to the half width of the absorption line
C. The half width of the absorption line should be smaller than the half width of the emission line of the light source
D. The monochromator can distinguish the emission spectrum, which means that the monochromator must have a very high resolution
In the complexometric titration with EDTA titrant, to determine the content of Al3+, an excessive amount of EDTA standard solution should be added first to produce Al3+-EDTA, and then the remaining EDTA standard solution should be titrated with Zn2+ standard solution. Finally, the content of Al3+ should be calculated from the consumed Zn2+ and EDTA. This method belongs to（ ）
A. indirect titration method
B. direct titration method
C. back titration
D. displacement titration
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