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Chapter 18: Q9 P (page 456)
18-9 Why does a compound whose visible absorption maximum is at 480 nm (blue-green) appear to be red?
The Transmitted light will be complement of the color of absorption at 480 nm.
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In formaldehyde, the transition occurs at 397 nm,and the transition comes at 355 nm. What is the difference in energy (kJ/mol) between the andstates? This difference is due to the different electron spins in the two states.
What is the difference between fluorescence and phosphorescence?
When I was a boy, Uncle Wilbur let me watch as he analyzed the iron content of runoff from his banana ranch. A 25.0 - mLsample was acidified with nitric acid and treated with excess KSCN to form a red complex. (KSCN itself iscolorless.) The solution was diluted to 100.0mLand put in a variable-pathlength cell. For comparison, a 10.0 - mLreference sample ofwas treated with andand diluted to. The reference was placed in a cell with a 1.00 - mL light path. The runoff sample exhibited the same absorbance as the reference when the path length of the runoff cell was 2.48cm. What was the concentration of iron in Uncle Wilbur鈥檚 runoff?
(a) A solution of compound A exhibited an absorbance of 0.624 at 238nmin a 1.000 cmcuvet; a blank solution containing only solvent had an absorbance of 0.029at the same wavelength. Find the molar absorptivity of compound A.
(b) The absorbance of an unknown solution of compound A in the same solvent and cuvet was 0.375 at 238 nm. Find the concentration of A in the unknown.
(c) A concentrated solution of compound A in the same solvent was diluted from an initial volume ofto a final volume of 25.00mLand then had an absorbance of 0.733. What is the concentration of A in the concentrated solution?
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?
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