6.4 The polymerization of methyl methacrylate (1.0 M in benzene) is carried out using a photosensitizer and 3130 Å light from a mercury lamp. If the quantum yield for radical production in this system is 0.50 and light is absorbed by the system at the rate of 10° ergs/L-s, calculate the rate of initiation. [Ans. 2.6x10-8 mol L-s-]

6.4 The polymerization of methyl methacrylate (1.0 M in benzene) is carried out using a photosensitizer and 3130 Å light from a mercury lamp. If the quantum yield for radical production in this system is 0.50 and light is absorbed by the system at the rate of 10° ergs/L-s, calculate the rate of initiation. [Ans. 2.6x10-8 mol L-s-]

Chemistry for Engineering Students

4th Edition

ISBN:9781337398909

Author:Lawrence S. Brown, Tom Holme

Publisher:Lawrence S. Brown, Tom Holme

Chapter11: Chemical Kinetics

Section: Chapter Questions

Problem 11.49PAE: The rate of photodecomposition of the herbicide piclo- ram in aqueous systems was determined by...

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6. Five reaction mixtures containing equal concentrations of an enzyme are made up to the substrate concentrations [S] indicated in the table below and the initial rates of the reaction (V) are measured. The experiment is repeated with an enzyme inhibitor I present at 0.22 mM in each reaction mixture. (a) Determine Km for the substrate and K, for the inhibitor. (b) Can you say anything about the type of the inhibitor? [S], mM V (µmol/min) (no I) V (µmol/min) (+ 0.22 mM I) 0.1 28 17 0.15 36 23 0.2 43 29 0.5 65 50 0.75 74 61
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,)?
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 the rate of formation of product (a) Initiation(b) Propagationf product (c) Termination
Where does the following first order equation K-0.693/t 1/2...(1) come from and why is this equation used.
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
A solution of 100 g/L acrylamide in methanol is polymerized at 25°C with 0.1 mol/L isobutyryl peroxide (initiator) whose half life is 9.0 h at this temperature and efficiency in methanol is 0.3. For acrylamide, k,?/k= 22 L mol-' s-l at 25°C and termination is by coupling alone. (a) What is the initial steady state rate of polymerization ? (b) Find the percentage conversion of monomers in the first 10 min of reaction in 1L of 2.5 solution? Acrylamide H H C-NH2 Hint : Find the initial concentration of monomer in mol/L [M] =(100 g/L)/(Molecular weight of acrylamide) Given the half-life time of the initiator used. Find dissociation rate constant of the initiator. In(2) Half-life t/2= kd 1/2 fks [1)* [M] k, 1/2 0.693/K. R = k, [M] kp 2 1/2 - In- %3D [M],
86) 203 (9) 7 302 (9) What is the Rate Law? 1.0L vessel => in which 10 mole * 1.0 mole 03 * 1.0 mole 02 What fraction of 03 will have reacted when the rate falls to one-fourth of its initial valuc?
The photochemical chlorination of chloroform,CHCl3 + Cl2 =====➔CCl4 + HClis believed to proceed by the following mechanism; (PHOTO BELOW) Derive the steady-state rate law for the production of carbon tetrachloride.
23.1b On the basis of the following proposed mechanism, account for the experimental fact that the rate law for the decomposition 2 N₂O5(g) → 4 NO₂(g) + O₂(g) is v=k[N₂O5]. (1) N₂O5NO2 + NO3 (2) NO₂ + NO3 → NO₂ + O₂ + NO (3) NO+N₂O5 → NO₂ + NO₂+NO₂ 23.2a A slightly different mechanism for the decomposition of N₂O5 from that in Exercise 23.1b has also been proposed. It differs only in the last step, which is replaced by (3) NO+NO3 →→ NO₂+NO₂ k3 Show that this mechanism leads to the same overall rate law. k₁, k₁ k₂ k3 23.2b Consider the following mechanism for the thermal decomposition of R₂: (1) R₂ → R+R (2) R+ R₂ → PB+R' (3) R' → PA+R (4) R+R PA + PB where R₂, PA, PB are stable hydrocarbons and R and R' are radicals. Find the dependence of the rate of decomposition of R₂ on the concentration of R₂. 16
Ll.67.
(1) (2) (3) (4) F₂0 + F₂0 F + F₂0 F + FO+F₂0 F₂ + FO OF+OF → O₂ + F + F F+ F + F₂0 F₂ + F₂0 d[F₂0] dt - → K₁ K2 K3 K4 Use the steady-state expression, for more than one species, to show that this mechanism is consistent with the experimental rate law shown below. The are 2 different effective rate constants, keff,1 and keff,2, each one applies to [F₂0] with a different reaction order. = keƒƒ,1[F₂0]² + keƒƒ,2[F₂0]3/2