Consider the following reaction:
At 25°C, the following two experiments were run, yielding the following data:
Experiment 1: [Y]0 = 3.0 M
[CH3X] (mol/L) | Time(h) |
7.08 × 10−3 | 1.0 |
4.52 × 10−3 | 1.5 |
2.23 × 10−3 | 2.3 |
4.76 × 10−4 | 4.0 |
8.44 × l0−5 | 5.7 |
2.75 × l0−5 | 7.0 |
Experiment 2: [Y]0 = 4.5 M
[CH3X] (mol/L) | Time(h) |
4.50 × 10−3 | 0 |
1.70 × 10−3 | 1.0 |
4.19 × 10−4 | 2.5 |
1.11 × 10−4 | 4.0 |
2.81 × l0−5 | 5.5 |
Experiments also were run at 85°C. The value of the rate constant at 85°C was found to be 7.88 × 108 (with the time in units of hours), where [CH3X]0 = 1.0 × 10−2 M and [Y]0 = 3.0 M.
a. Determine the rate law and the value of k for this reaction at 25°C.
b. Determine the half-life at 85°C.
c. Determine Ea for the reaction.
d. Given that the C8X bond energy is known to be about 325 kJ/mol, suggest a mechanism that explains the results in parts a and c.
Want to see the full answer?
Check out a sample textbook solutionChapter 11 Solutions
Chemistry: An Atoms First Approach
- 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+Fastarrow_forwardGaseous NO2 decomposes at 573 K. NO2(g) NO(g) + O2(g) The concentration of NO2 was measured as a function of time. A graph of 1/[NO2] versus time gives a straight line with a slope of 1.1 L/mol s. What is the rate law for this reaction? What is the rate constant?arrow_forwardAmmonia decomposes when heated according to the equation NH3(g) NH2(g) + H(g) The data in the table for this reaction were collected at a high temperature. Plot In [NH3] versus time and 1/[NH3] versus time. What is the order of this reaction with respect to NH3? Find the rate constant for the reaction from the slope.arrow_forward
- The decomposition of gaseous dimethyl ether at ordinary pressures is first-order. Its half-life is 25.0 minutes at 500 C: CH3OCH3(g) CH4(g) + CO(g) + H2(g) (a) Starting with 8.00 g of dimethyl ether, what mass remains (in grams) after 125 minutes and after 145 minutes? (b) Calculate the time in minutes required to decrease 7.60 ng (nanograms) to 2.25 ng. (c) What fraction of the original dimethyl ether remains after 150 minutes?arrow_forwardThe isomerization of cyclopropane, C3H6, is believed to occur by the mechanism shown in the following equations: C3H6+C3H5k1C3H6+C3H6(Step1)C3H6k2C2=CHCH3(Step2) Here C3H6 is an excited cyclopropane molecule. At low pressure, Step 1 is much slower than Step 2. Derive the rate law for this mechanism at low pressure. Explain.arrow_forwardThe half-life of tritium, 3H, is 12.26 years. Tritium is the radioactive isotope of hydrogen. (a) What is the rate constant for the radioactive decay of tritium, in y1 and s1? (b) What percentage of the original tritium is left after 61.3 years?arrow_forward
- Rank the following in order of increasing reaction rate. (a) Dynamite exploding (b) Iron rusting (c) Paper burningarrow_forwardThe thermal decomposition of nitryl chloride, NO2Cl, 2NO2Cl(g)2NO2(g)+Cl2(g) is thought to occur by the mechanism shown in the following equations: NO2Clk1NO2+Cl(slowstep)NO2Cl+Clk2NO2+Cl2(faststep) What rate law is predicted by this mechanism?arrow_forwardBased on the kinetic theory of matter, what would the action of a catalyst do to a reaction that is the reverse of some reaction that we say is catalyzed?arrow_forward
- Nitrogen monoxide reacts with oxygen to give nitrogen dioxide. 2NO(g)+O2(g)2NO2(g) The rate law is [NO]/t = k[NO]2[O2], where the rate constant is 1.16 103 L2/(mol2 s) at 339oC. A vessel contains NO and O2 at 339oC. The initial partial pressures of NO and O2 arc 155 mmHg and 345 mmHg, respectively. What is the rate of decrease of partial pressure of NO (in mmHg per second)? (Hint: From the ideal gas law, obtain an expression for the molar concentration of a particular gas in terms of its partial pressure.)arrow_forwardHydrogen iodide decomposes when heated, forming H2(g) and I2(g). The rate law for this reaction is [HI]/t = k[HI]2. At 443C, k = 30. L/mol min. If the initial HI(g) concentration is 1.5 102 mol/L, what concentration of HI(g) will remain after 10. minutes?arrow_forward
- Chemistry & Chemical ReactivityChemistryISBN:9781133949640Author:John C. Kotz, Paul M. Treichel, John Townsend, David TreichelPublisher:Cengage LearningChemistry & Chemical ReactivityChemistryISBN:9781337399074Author:John C. Kotz, Paul M. Treichel, John Townsend, David TreichelPublisher:Cengage LearningGeneral Chemistry - Standalone book (MindTap Cour...ChemistryISBN:9781305580343Author:Steven D. Gammon, Ebbing, Darrell Ebbing, Steven D., Darrell; Gammon, Darrell Ebbing; Steven D. Gammon, Darrell D.; Gammon, Ebbing; Steven D. Gammon; DarrellPublisher:Cengage Learning
- Chemistry for Engineering StudentsChemistryISBN:9781337398909Author:Lawrence S. Brown, Tom HolmePublisher:Cengage LearningChemistry: The Molecular ScienceChemistryISBN:9781285199047Author:John W. Moore, Conrad L. StanitskiPublisher:Cengage LearningChemistryChemistryISBN:9781305957404Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCostePublisher:Cengage Learning