(a) Consider the following (overall) chemical reactionkABThe experimentally determined rate law expression reads: rate = k[A]. At 30 °C, thevalue of k is 3 x 10-4 s¹. Let the initial concentration of A be [A]0 = 0.75 mol L-¹. Thereaction should proceed until only 2% of the initial amount of A is present in thereaction mixture.(i) How long will this take at 30°C?(ii) What value would the rate coefficient k have to be, in order for theconcentration of A to reach the 2% level in 1 hour?(iii) At what temperature will k reach the value you calculated in (ii) assumingthat the activation energy is 40 kJ mol¹?

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Answered: (a) Consider the following (overall)…

Chemistry: Matter and Change

1st Edition

ISBN:9780078746376

Author:Dinah Zike, Laurel Dingrando, Nicholas Hainen, Cheryl Wistrom

Publisher:Dinah Zike, Laurel Dingrando, Nicholas Hainen, Cheryl Wistrom

Chapter16: Reaction Rates

Section: Chapter Questions

Problem 69A

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Azomethane decomposes into nitrogen and ethane at high temperatures according to the following equation: (CH3)2N2(g)N2(g)+C2H6(g)The rate of the reaction is followed by monitoring the disappearance of the purple color due to iodine. The following data are obtained at a certain temperature. (a) By plotting the data, show that the reaction is first-order. (b) From the graph, determine k. (c) Using k, find the time (in hours) that it takes to decrease the concentration to 0.100 M. (d) Calculate the rate of the reaction when [ (CH3)2N2 ]=0.415M.
Diethylhydrazine reacts with iodine according to the following equation: Â (C2H5)2(NH)2(l)+I2(aq)(C2H5)2N2+2HI(aq)The rate of the reaction is followed by monitoring the disappearance of the purple color due to iodine. The following data are obtained at a certain temperature. (a) What is the order of the reaction with respect to diethylhydrazine, iodine, and overall? (b) Write the rate expression of the reaction. (c) Calculate k for the reaction. (d) What must [(C2H5)2] be so that the rate of the reaction is 5.00104mol/Lh when [ I2 ]=0.500M?
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The label on a bottle of 3% (by volume) hydrogen peroxide, H2O2, purchased at a grocery store, states that the solution should be stored in a cool, dark place. H2O2decomposes slowly over time, and the rate of decomposition increases with an increase in temperature and in the presence of light. However, the rate of decomposition increases dramatically if a small amount of powdered MnO- is added to the solution. The decomposition products are H2O and O2. MnO2 is not consumed in the reaction. Write the equation for the decomposition of H2O2. What role does MnO2 play? In the chemistry lab, a student substituted a chunk of MnO2 for the powdered compound. The reaction rate was not appreciably increased. WTiat is one possible explanation for this observation? Is MnO2 part of the stoichiometry of the decomposition of H2O2?
The reaction NO(g) + O,(g) — NO,(g) + 0(g) plays a role in the formation of nitrogen dioxide in automobile engines. Suppose that a series of experiments measured the rate of this reaction at 500 K and produced the following data; [NO] (mol L ’) [OJ (mol L 1) Rate = -A[NO]/Af (mol L_1 s-1) 0.002 0.005 8.0 X 10"'7 0.002 0.010 1.6 X 10-'6 0.006 0.005 2.4 X IO-'6 Derive a rate law for the reaction and determine the value of the rate constant.
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The hydrolysis of the sugar sucrose to the sugars glucose and fructose, C12H22O11+H2OC6H12O6+C6H12O6 follows a first-order rate equation for the disappearance of sucrose: Rate =k[C12H22O11] (The products of the reaction, glucose and fructose, have the same molecular formulas but differ in the arrangement of the atoms in their molecules.) (a) In neutral solution, k=2.11011s1 at 27 C and 8.51011s1 at 37 C. Determine the activation energy, the frequency factor, and the rate constant for this equation at 47 C (assuming the kinetics remain consistent with the Arrhenius equation at this temperature). (b) When a solution of sucrose with an initial concentration of 0.150 M reaches equilibrium, the concentration of sucrose is 1.65107M . How long will it take the solution to reach equilibrium at 27 C in the absence of a catalyst? Because the concentration of sucrose at equilibrium is so low, assume that the reaction is irreversible. (c) Why does assuming that the reaction is irreversible simplify the calculation in pan (b)?
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