Learning Materials
Features
Discover
Chapter 18: Q35P (page 459)
Consider a molecule that can fluoresce from the S1 state and phosphoresce from the T1 state. Which is emitted at longer wavelength, fluorescence or phosphorescence? Make a sketch showing absorption, fluorescence, and phosphorescence on a single spectrum.
Over 30 million students worldwide already upgrade their learning with 91影视!
All the tools & learning materials you need for study success - in one app.
Get started for free
(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?
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 鈥揳 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?
If a sample for spectrophotometric analysis is placed in a 10 - cmcell, the absorbance will be 10times greater than the absorbance in a 1 - cmcell. Will the absorbance of the reagent-blank solution also be increased by a factor of 10?
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?
18-8: What is an absorption spectrum?
What do you think about this solution?
We value your feedback to improve our textbook solutions.
Explanations 
Textbooks 
Flashcards 
91影视 AI 
Notes 
Study Plans 
Study Sets 
Find a degree 
Magazine