In a study of the decomposition of ammonia on a platinum surface at 856 °C NH3-1/2 N₂ + 3/2 H₂ the following data were obtained: [NH3], M seconds 5.79x10-3 0 2.90x10-3 998 1.45x10-3 7.25x10-4 1.50x10³ 1.75x10³ Hint: It is not necessary to graph these data. (1) The observed half life for this reaction when the starting concentration is 5.79x10-3 M is starting concentration is 2.90x10-³ M is (2) The average rate of disappearance of NH3 from t = 0 s to t = 998 s is (3) The average rate of disappearance of NH3 from t = 998 s to t = 1.50x10³ s is (4) Based on these data, the rate constant for this order reaction is M s 1. M s 1. Ms¹. s and when the

In a study of the decomposition of ammonia on a platinum surface at 856 °C NH3-1/2 N₂ + 3/2 H₂ the following data were obtained: [NH3], M seconds 5.79x10-3 0 2.90x10-3 998 1.45x10-3 7.25x10-4 1.50x10³ 1.75x10³ Hint: It is not necessary to graph these data. (1) The observed half life for this reaction when the starting concentration is 5.79x10-3 M is starting concentration is 2.90x10-³ M is (2) The average rate of disappearance of NH3 from t = 0 s to t = 998 s is (3) The average rate of disappearance of NH3 from t = 998 s to t = 1.50x10³ s is (4) Based on these data, the rate constant for this order reaction is M s 1. M s 1. Ms¹. s and when the

Principles of Modern Chemistry

8th Edition

ISBN:9781305079113

Author:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler

Publisher:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler

Chapter18: Chemical Kinetics

Section: Chapter Questions

Problem 7P

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The rate of photodecomposition of the herbicide piclo- ram in aqueous systems was determined by exposure to sunlight for a number of days. One such experiment produced the following results. (Data from R.T. Hedlun and C.R. Youngson, “The Rates of Photodecomposition of Picloram in Aqueous Systems," Fate of Organic Pesticides in tbe Aquatic Environment, Advances in Chemistry Series, #111, American Chemical Society (1972), 159—172.) Exposure Time, t (days) [Pidoram] (mol L_1) 0 4.14 X 10-6 7 3.70 X 10-6 14 3.31 X 10-6 21 2.94 X 10~6 28 2.61 X 10~6 35 2.30 X 10-6 42 2.05 X 10-6 49 1.82 X 10"6 56 1.65 X 10-6 Determine the order of reaction, the rate constant, and the half-life for the photodecomposition of picloram.
The rate of the reaction O(g)+NO2(g)NO(g)+O2(g) was studied at a certain temperature. a. In one experiment, NO2 was in large excess, at a concentration of 1.0 1013 molecules/cm3 with the following data collected: Time(s) [O](atoms/cm3) 0 5.0 109 1.0 102 1.9 109 2.0 102 6.8 108 3.0 102 2.5 108 What is the order of the reaction with respect to oxygen atoms? b. The reaction is known to be first order with respect to NO2 Determine the overall rate law and the value of the rate constant.
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)?
Define stability from both a kinetic and thermodynamic perspective. Give examples to show the differences in these concepts.
Consider the first-order decomposition of phosgene at a certain temperature. COCl2(g)productsIt is found that the concentration of phosgene is 0.0450 M after 300 seconds and 0.0200 M after 500 seconds. Calculate the following: (a) the rate constant at the temperature of the decomposition (b) the half-life of the decomposition (c) the intial concentration of phosgene
The decomposition of NH3 to N2 and H2 was studied on two surfaces: Surface Ea (kJ/mol) W 163 Os 197 Without a catalyst, the activation energy is 335 kJ/mol. a. Which surface is the better heterogeneous catalyst for the decomposition of NH3? Why? b. How many times faster is the reaction at 298 K on the W surface compared with the reaction with no catalyst present? Assume that the frequency factor A is the same for each reaction. c. The decomposition reaction on the two surfaces obeys a rate law of the form Rate=k[NH3][H2] How can you explain the inverse dependence of the rate on the H2 concentration?
The thermal decomposition of diacetylene, C4H2, was studied at 950 C. Use the following data (K. C. Hou and H. B. Palmer, Journal of Physical Chemistry. Vol. 60, p. 858, 1965) to determine the order of the reaction.
Experiments have shown that the average frequency of chirping by a snowy tree cricket (Oecanthus fultoni) depends on temperature as shown in the table. Chirping Rate (per min) Temperature (C) 178 25.0 126 20.3 100. 17.3 What is the apparent activation energy of the process that controls the chirping? What is the rate of chirping expected at a temperature of 7.5C?
For the zero-order decomposition of ammonia on tungsten NH3(g) W 12 N2(g)+32 H2(g)the rate constant is 2.08104mol/Ls. (a) What is the half-life of a 0.250 M solution of ammonia? (b) How long will it take for the concentration of ammonia to drop from 1.25 M to 0.388 M?