Ch. 12-13 Hon Chem HW A4) #73 HC 2 of 4

A3) #73 HC 3 of 4

A5) #73 HC 4 of 4

A6) #74 HC 2 of 5

12B1) #74 HC 3 of 5

B4) A certain reaction has the following general form: aA → bB #74 HC 4 of 5 At a particular temperature, concentration versus time data were collected for this reaction. A plot of 1/[A] versus time resulted in a straight line with a slope of +3.60 X10-2 M-1∙s-1. The initial concentration, [A]o, was equal to 2.80 X10-3 M. a) Determine the rate law and the value of the rate constant. b) Calculate the half-life for this reaction. c) How much time is required for the concentration of A to decrease to 7.00 X10-4 M?

B5) The decomposition of ethanol (C2H5OH) on an alumina (Al2O3) surface, C2H5OH(g) → C2H4(g) + H2O(g), was studied at 600 K. Concentration versus time data were collected for this reaction. A plot of [A] versus time resulted in a straight line with a slope of -4.00 X10-5 M∙s-1. a) Determine the rate law and the value of the rate constant. b) If the initial concentration of C2H5OH was 1.25 X10-2 M, calculate the half-life for this reaction. c) How much time is required for all of the 1.25 X10-2 M C2H5OH to decompose?

B8) The radioactive isotope 32P decays by first-order kinetics and has a half-life of 14.3 days. How long does it take for 95.0% of a sample of 32P to decay?

12B3) #75 HC 2 of 6

C2) A proposed mechanism for a reaction is C4H9Br →C4H9

+1 + Br-1 slow C4H9

+1 + H2O →C4H9OH2+1 fast

C4H9OH2+1 + H2O → C4H9OH + H3O+1 fast

a) Write the rate law. b) What is the overall reaction for this process? c) What are the intermediates in the proposed mechanism?

C3) The mechanism for the reaction of nitrogen dioxide #75 HC 5 of 6 with carbon monoxide is thought to be: NO2 + NO2 → NO3 + NO slow NO3 + CO → NO2 + CO2 fast a) Write the rate law. b) What is the overall reaction for this process?

D1)

For the above reaction profile, indicate: a) the positions of the reactants and the products. b) the activation energy. c) ∆E for the reaction. d) whether the reaction is endothermic or exothermic.

D2) Draw a rough sketch of the reaction profile for each of the following cases: a) ∆E = +10 kj/mol Ea = 25 kj/mol

b) ∆E = -10 kj/mol Ea = 50 kj/mol #75 HC 6 of 6

C4) The below mechanisms are proposed to explain the kinetics for the following reaction: 2 H2(g) + 2 NO(g) → N2(g) + 2 H2O(g), having an observed rate law of Rate = k [NO]2 [H2]1 Which of the following mechanisms explain the above reaction? Explain. Mechanism 1: 2 H2(g) + 2 NO(g) → N2(g) + 2 H2O(g) Mechanism 2: H2(g) + NO(g) → H2O(g) + N(g) slow N(g) + NO(g) → N2(g) + O (g) fast H2(g) +O(g) → H2O(g) fast Mechanism 3: H2(g) + 2 NO(g) → N2O(g) + H2O(g) slow N2O(g) + H2(g) → N2(g) + H2O(g) fast

D3) #76 HC 2 of 6

D4) At 25oC the first-order rate constant for a reaction is 2.0 X103 s-1. #76 HC 3 of 6 The activation energy is 15.0 kj/mol. What is the value of the rate constant at 75oC?

D5) A first-order reaction has rate constants of #76 HC 4 of 6 4.6 X10-2 s-1 and 8.1 X10-2 s-1 at 0.0oC and 20.oC, respectively. What is the value of the activation energy?

E1) One mechanism for the destruction of ozone in the upper atmosphere is O3(g) + NO(g) → NO2(g) + O2(g) slow NO2(g) + O(g) → NO(g) + O2(g) fast O3(g) + O(g) → 2 O2(g) overall reaction a) Which species is an intermediate?

b) Which species is a catalyst? {A catalyst will be a reactant that will reappear as a product, so that it will cancel out in the reaction. An intermediate will not be a reactant or a product.}

c) Ea for the catalyzed reaction #76 HC 5 of 6 O3(g) + O(g) → 2 O2(g) is 11.9 kj. Ea for the same reaction, when it is uncatalyzed is 14.0 kj. What is the ratio of the rate constant for the catalyzed reaction to that of the uncatalyzed reaction at 25oC? Assume the frequency factor A is the same in both reactions.

D7) Chemists commonly use a rule of thumb that an increase of 10. K #77 HC 2 of 4 in temperature doubles the rate of a reaction. What must the activation energy be for this statement to be true for a temperature increase from 25oC to 35oC?

e) 2 Fe(s) + 3/2 O2(g) ↔ Fe2O3(s)

f) CO2(g) + MgO(s) ↔ MgCO3(s)

A1) At high temperatures, elemental nitrogen and oxygen react with each other to form nitrogen monoxide: N2(g) + O2(g) ↔ 2 NO(g) Suppose the system is analyzed at a particular temperature, and at equilibrium the concentrations are found to be [N2] = 0.041 M, [O2] = 0.0078 M, and [NO] = 4.7 X10- 4 M. Calculate the value of K for the reaction.

A4) The following equilibrium pressures at a certain temperature were observed for the reaction: #77 HC 4 of 4 2 NO2(g) ↔ 2 NO(g) + O2(g) PNO2 = 0.55 atm, PNO = 6.5 X10-5 atm, PO2 = 4.5 X10-5 atm Calculate the value for the equilibrium constant, Kp, at this temperature.

A6) At 25oC, K = 3.7 X109 for the reaction: CO(g) + Cl2(g) ↔ COCl2(g) Calculate Kp at this temperature.

B2) The reaction H2(g) + I2(g) ↔ 2 HI(g) has Kp = 45.9 at 763 K. #78 HC 1 of 4 A particular equilibrium mixture at that temperature contains HI gas at a partial pressure of 4.00 atm and H2 gas at a partial pressure of 0.200 atm. What is the pressure of I2?

B6) At 25oC, K = 0.090 for the reaction: #78 HC 2 of 4 H2O(g) + Cl2O(g) ↔ 2 HOCl(g) Calculate the concentrations of all species at equilibrium for each of the following cases. a) 1.0 g H2O and 2.0 g Cl2O are mixed in a 1.0 L flask.

B5) At 2200oC, Kp = 0.050 for the reaction: #78 HC 4 of 4 N2(g) + O2(g) ↔ 2 NO(g) What is the partial pressure of NO in equilibrium with N2 and O2, if the initial pressures of N2 and O2 were 0.80 atm and 0.20 atm, respectively?

C1) An important reaction in the commercial production of hydrogen is: #79 HC 1 of 6 CO(g) + H2O(g) ↔ H2(g) + CO2(g) How will this system at equilibrium shift {right or left} in each of the following cases? a) Gaseous carbon dioxide is removed. b) Water vapor is added. c) The pressure is increased by adding helium gas. d) The temperature is increased. (This reaction is exothermic.) e) The pressure is increased by decreasing the volume of the reaction container.

B7) At 35oC, K = 1.6 X10-5 for the reaction: #79 HC 2 of 6 2 NOCl(g) ↔ 2 NO(g) + Cl2(g) Calculate the concentrations of all species at equilibrium for each of the following cases. a) 2.0 mol pure NOCl is placed in a 2.0 L flask.

b) 1.0 mol NOCl and 1.0 mol NO are mixed in a #79 HC 3 of 6 1.0 L flask.

B3) At a particular temperature, K = 3.75 for the reaction: #79 HC 5 of 6 SO2(g) + NO2(g) ↔ SO3(g) + NO(g) If all four gases had initial concentrations of 0.800 M, calculate the equilibrium concentrations of the gases.

B4) At a particular temperature, K = 1.00 X102 for the reaction: H2(g) + I2(g) ↔ 2 HI(g) #79 HC 6 of 6 In an experiment, 1.00 mol H2, 1.00 mol I2, and 1.00 mol HI are introduced into a 1.00 L container. Calculate the concentrations of all species (all compounds) when equilibrium is reached.