b. Chemical C 4. In the following reaction, the initial rate of change in the concentration of A was 0.253 M/s. 5A + 2B → 3C + D What is the initial rate of change in the concentration of: a. Chemical B C. Chemical D Time The following initial ra black

b. Chemical C 4. In the following reaction, the initial rate of change in the concentration of A was 0.253 M/s. 5A + 2B → 3C + D What is the initial rate of change in the concentration of: a. Chemical B C. Chemical D Time The following initial ra black

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 11.40PAE: In Exercise 11.39, if the initial concentration of N2Oj is 0.100 .\1. how long will it take for the...

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Ozone, O3, in the Earths upper atmosphere decomposes according to the equation 2 O3(g) 3 O2(g) The mechanism of the reaction is thought to proceed through an initial fast, reversible step followed by a slow, second step. Step 1: Fast, reversible O3(g) O2(g) + O(g) Step 2: Slow O3(g) + O(g) 2 O2(g) (a) Which of the steps is rate-determining? (b) Write the rate equation for the rate-determining step
You are studying the kinetics of the reaction H2(g) + F2(g) 2HF(g) and you wish to determine a mechanism for the reaction. You run the reaction twice by keeping one reactant at a much higher pressure than the other reactant (this lower-pressure reactant begins at 1.000 atm). Unfortunately, you neglect to record which reactant was at the higher pressure, and you forget which it was later. Your data for the first experiment are: Pressure of HF (atm) Time(min) 0 0 0.300 30.0 0.600 65.8 0.900 110.4 1.200 169.1 1.500 255.9 When you ran the second experiment (in which the higher pressure reactant was run at a much higher pressure), you determine the values of the apparent rate constants to be the same. It also turns out that you find data taken from another person in the lab. This individual found that the reaction proceeds 40.0 times faster at 55C than at 35C. You also know, from the energy-level diagram, that there are three steps to the mechanism, and the first step has the highest activation energy. You look up the bond energies of the species involved and they are (in kJ/mol): H8H (432), F8F (154), and H8F (565). a. Sketch an energy-level diagram (qualitative) that is consistent with the one described previously. Hint: See Exercise 106. b. Develop a reasonable mechanism for the reaction. c. Which reactant was limiting in the experiments?
The reaction 2 NO(g) + 2 H2(g) N2(g) + 2 H2O(g) was studied at 904 C, and the data in the table were collected. (a) Determine the order of the reaction for each reactant. (b) Write the rate equation for the reaction. (c) Calculate the rate constant for the reaction. (d) Find the rate of appearance of N2 at the instant when [NO] = 0.350 mol/L and [H] = 0.205 mol/L.
Kinetics I Consider the hypothetical reaction A(g) + 2B(g) h C(g). The four containers below represent this reaction being run with different initial amounts of A and B. Assume that the volume of each container is 1.0 L. The reaction is second order with respect to A and first order with respect to B. a Based on the information presented in the problem, write the rate law for the reaction. b Which of the containers, W, X, Y, or Z, would have the greatest reaction rate? Justify your answer. c Which of the containers would have the lowest reaction rate? Explain. d If the volume of the container X were increased to 2.0 L, how would the rate of the reaction in this larger container compare to the rate of reaction run in the 1.0-L container X? (Assume that the number of A and B atoms is the same in each case.) e If the temperature in container W were increased, what impact would this probably have on the rate of reaction? Why? f If you want to double the rate of reaction in container X, what are some things that you could do to the concentration(s) of A and B? g In which container would you observe the slowest rate of formation of C? h Assuming that A and B are not in great excess, which would have the greater impact on the rate of reaction in container W: removing a unit of B or removing a unit of A? Explain. i Describe how the rate of consumption of A compares to the rate of consumption of B. If you cannot answer this question, what additional information do you need to provide an answer? j If the product C were removed from the container as it formed, what effect would this have on the rate of the reaction?
In Exercise 11.39, if the initial concentration of N2Oj is 0.100 .\1. how long will it take for the concentration to drop to 0.0100 times its original value? The decomposition of N2O5 in solution in carbon tetrachloride is a first-order reaction: 2N2O5—»4NO2 + O2 The rate constant at a given temperature is found to be 5.25 X 10-4 s-’. If the initial concentration of N2O5 is 0.200 M, what is its concentration after exactly 10 minutes have passed?
At 573 K, gaseous NO2(g) decomposes, forming NO(g) and O2(g). If a vessel containing NO2(g) has an initial concentration of 1.9 102 mol/L, how long will it take for 75% of the NO2(g) to decompose? The decomposition of NO2(g) is second-order in the reactant and the rate constant for this reaction, at 573 K, is 1.1 L/mol s.
Candle wax is a mixture of hydrocarbons. In the reaction of oxygen with candle w ax in Figure 11.2, the rate of consumption of oxygen decreased with time after the flask was covered, and eventually' the flame went out. From the perspective of the kinetic-molecular theory, describe what is happening in the flask. FIGURE 11.2 When a candle burns in a closed container, the flame will diminish and eventually go out. As the amount of oxygen present decreases, the rate of combustion will also decrease. Eventually, the rate of combustion is no longer sufficient to sustain the flame even though there is still some oxygen present in the vessel.
The following statements relate to the reaction for the formation of HI: H2(g) + I2(g) -* 2 HI(g) Rate = it[HJ [I2J Determine which of the following statements are true. If a statement is false, indicate why it is incorrect. The reaction must occur in a single step. This is a second-order reaction overall. Raising the temperature will cause the value of k to decrease. Raising the temperature lowers the activation energy' for this reaction. If the concentrations of both reactants are doubled, the rate will double. Adding a catalyst in the reaction will cause the initial rate to increase.
The following statements relate to the reaction for the formation of HI: H2(g) + I2(g) 2 HI(g)Rate = k[H2][I2] Determine which of the following statements are true. If a statement is false, indicate why it is incorrect. (a) The reaction must occur in a single step. (b) This is a second-order reaction overall. (c) Raising the temperature will cause the value of k to decrease. (d) Raising the temperature lowers the activation energy for this reaction. (e) If the concentrations of both reactants are doubled, the rate will double. (f) Adding a catalyst in the reaction will cause the initial rate to increase.
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?
Iodomethane (CH3I) is a commonly used reagent in organic chemistry. When used properly, this reagent allows chemists to introduce methyl groups in many different useful applications. The chemical does pose a risk as a carcinogen, possibly owing to iodomethanes ability to react with portions of the DNA strand (if they were to come in contact). Consider the following hypothetical initial rates data: [DNA]0 ( mol/L) [CH3I]0 ( mol/L) Initial Rate (mol/Ls) 0.100 0.100 3.20 104 0.100 0.200 6.40 104 0.200 0.200 1.28 103 Which of the following could be a possible mechanism to explain the initial rate data? MechanismIDNA+CH3IDNACH3++IMechanismIICH3ICH3++ISlowDNA+CH3+DNACH3+Fast