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Chapter 18: Q36P (page 460)
What is the difference between a fluorescence excitation spectrum and a fluorescence emission spectrum? Which one resembles an absorption spectrum?
The fluorescence excitation spectrum resembles an absorption spectrum.
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Preparing standards for a calibration curve.
(a) How much ferrous ethylene diammonium sulfateshould be dissolved in a 500mL volumetric flask withto obtain a stock solution with?
(b) When making stock solution (a), you actually weighed out 1.627 g of reagent. What is the Fe concentration in role="math" localid="1668357579931" ?
(c) How would you prepare 500 mL of standard containing 1,2,3,4, andinfrom stock solution (b) using any Class A pipets from Table 2-4 with only 500 -mL volumetric flasks?
(d) To reduce the generation of chemical waste, describe how you could prepare 50 mL of standard containing, andinfrom stock solution (b) by serial dilution using any Class A pipets from Table 2-3 with only 50mL volumetric flasks?
In a different titration, the absorbance after adding 75 mL of ferric nitrilo-triacetate to 1.500 mL of Apo transferrin was 0.222. Find the corrected absorbance.
What is the wavelength, wavenumber, and name of radiation with an energy of 100 kJ/mol?
Characteristic orange light produced by sodium in a flame is due to an intense emission called the sodium D line, which actually a doublet, with wavelength (measured in vacuum) of 589.157 88 and 589.755 37 nm. The index of refraction of air at a wavelength near 589 nm is 1.000 292 6. Calculate the frequency, wavelength, and wavenumber of each component of the D line, measured in air.
Nitrite ion, is a preservative for bacon and other foods, but it is potentially carcinogenic. A spectrophotometric determination ofmakes use of the following reactions
Here is an abbreviated procedure for the
determination:
1. To 50.0ml of unknown solution containing nitrite is added 1.00mL of sulfanilic acid solution.
2. After 10min , 2.00mL of 1 –a minonaphthalene solution and 1.00 mL of buffer are added.
3. After 15 min, the absorbance is read at 520 nm in a 5.00-cm cell.
The following solutions were analyzed:
A. 50.0 mL of food extract known to contain no nitrite (that is, a negligible amount); final absorbance =0.153.
B. 50.0mL of food extract suspected of containing nitrite; final absorbance \(=0.622\).
C. Same as B, but with added to the 50.0-mL sample; final absorbance =0.967.
(a) Calculate the molar absorptivity, of the colored product. Remember that a \(5.00\)-cm cell was used.
(b) How many micrograms ofwere present in 50.0mL of food extract?
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