(d) The first-order rate constants for the fluorescence and phosphorescence of molecule X are 4.5 x 107 s' and 0.50 s', respectively. Briefly explain the large order of magnitude difference in the rate constant values. (c) Explain how long (in s) it takes for 1.0% of fluorescence and phosphorescence to occur following termination of excitation.

(d) The first-order rate constants for the fluorescence and phosphorescence of molecule X are 4.5 x 107 s' and 0.50 s', respectively. Briefly explain the large order of magnitude difference in the rate constant values. (c) Explain how long (in s) it takes for 1.0% of fluorescence and phosphorescence to occur following termination of excitation.

Principles of Instrumental Analysis

7th Edition

ISBN:9781305577213

Author:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Publisher:Douglas A. Skoog, F. James Holler, Stanley R. Crouch

Chapter15: Molecular Luminescence Spectrometry

Section: Chapter Questions

Problem 15.15QAP: The following lifetimes were measured for the chloride quenching of quinine sulfate given in Example...

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The following lifetimes were measured for the chloride quenching of quinine sulfate given in Example 15-1.The fluorescence intensities are given in the example. (a) Plot fluorescence intensity versus [Cl-]. (b) Plot the ratio of intensity to lifetime, F- versus [Cl-]. (c) Develop a normalization factor to correct the measured fluorescence intensity to that of the solution without quencher. (d) Plot on the same graph Fversus [Cl-] and Fcorr versus (CI-].
The fluorescence of a fluorophore is quenched in the presence of iodide ions. (i) Would the fluorescence quantum yield in the presence of iodide be larger or smaller than the fluorescence quantum yield in the absence of iodide? Explain your answer. (ii) Would the fluorescence lifetime of the fluorophore in the presence of iodide be longer or shorter than the lifetime in the absence of iodide? Explain your answer.
The degradation of the antibiotic clindamycin stored at 343 K in aqueous solution at pH 4 is found to be first order with a rate constant of 2.49 x 10−7 s −1. Over the temperature range 320 K to 360 K theactivation energy was found to be 123.3 kJ mol−1. (a) Calculate the rate constant at 325 K.(b) The threshold for product safety is 1% degradation. At 295 K the time taken for 1% of the antibiotic to degrade is found to be close to 0.01/ k. Comment on the shelf-life of the drug.
Give the equation for quantum yield j. rate of formation of the singlet state rate of ith decay mechanism rate of ith decay mechanism rate of removal of the singlet state rate of ith decay mechanism rate of formation of the singlet state rate of removal of the singlet state rate of ith decay mechanism Step 4 of 6 Give the quantum yield ;. (Use the following as necessary: kj, k1, k2, k3, and t.) k1 + k, + k = ki 3 k1 + k2 + k3 Recalling the relationship between the overall rate constant, k, and the mean lifetime, T, give the quantum yield D; in terms of T and Tj. (Use the following as necessary: T and T;) i Step 5 of 6 (c) If T1 = 1×10-7 s, T2 = 4x10-8 s, and T3 = 1x10-8 s, calculate the lifetime of the singlet state and the quantum yield for the path that has T2. (Enter an unrounded value with at least 3 digits.) 1 using the equation given in (b). Calculate = 7.407e-9 s-1 Solve for T, the lifetime of the singlet state. T = .185175 X S Submit
Consider the following chain mechanism(a) AH →A•+ H• K1(b) A → B• + C K2(c) B• + H• → P K3Identify the steps in the chain and use the steady-state approximation to determine therate of formation of product(a) Initiation(b) Propagation product(c) Termination
In a free radical polymerization that proceeds without chain transfer, what is the effect of (a) increasing the monomer concentration by a factor of four at constant initiator concentration and (b) increasing the initiator concentration by a factor of four at constant monomer concentration on each of the following: (i) the total radical concentration at steady state ([M•]) (ii) the rate of polymerization (Rp) (iii) the number average degree of polymerization (X,)?
An excited ozone molecule, 03*, in the atmosphere can undergo one of the following reactions, Оз (1) fluorescence 03 O + 02 (2) decomposition 03" + M - 03 + M (3) deactivation, where M is an inert molecule, the rate constant for the fluorescence reaction is k1, the rate constant for the decomposition reaction is k2, and the rate constant for the deactivation reaction is k3. Write a simplified expression for the fraction, X, of ozone molecules undergoing decomposition in terms of the rate constants. (Use the following as necessary: k1, k2, k3, co for [03*], and CM for [M].) X =
4. Which of the following best describes the timescales of fluorescence and phosphorescence? (b) Tfluorphos (d) there is no general trend Tfluor > Tphos Tfluor Tphos In 1-2 sentences, explain your reasoning:
Define the following terms :(a) Pseudo first order reaction.(b) Half life period of reaction (t1/2).
Consider the following chain mechanism (a) AH →A•+ H• K1(b) A → B• + C K2(c) B• + H• → P K3Identify the steps in the chain and use the steady state approximation to determine the rate of formation of product (a) Initiation(b) Propagationf product (c) Termination
In an experiment to measure the quantum yield of a photochemical reaction, the absorbing substance was exposed to 320. nm radiation from a(n) 96.3 W source for 39.9 min. The intensity of the transmitted radiation was 0.315 that of the incident radiation. As a result of irradiation, 0.108 mol of the absorbing substance decomposed. Evaluate the quantum yield.
How many intermediates are present in the proposed mechanism of lodine clock reaction? (note: disregard balancing) 103 (aq) + HSO3 (ag) >l'(ag) + 3HSO4 (aq) (slow) 103 (aq) + 6H (aq) + 51(aq) -> 312(ag) + 3H20() |2(aq) + HSO3 (aq) + H20) -> 21 (aq) + HSO4 (aq) + 2H* (aq) Overall Reaction: 2H* (ag) + 2103 (aq) + HSO3 (aq) -> 2HSO4 (aq) + 2H200 O a. 2 O b. 3 O C. 0 O d. 1