practice - Midterm 1: Practice Questions on Thermochemistry...

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Unformatted text preview: Midterm 1: Practice Questions on Thermochemistry and Chemical Kinetics MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) Which of the following is NOT used in the definition of standard enthalpy of formation? 1) _______ A) lements in standard states e B) eat evolved at constant pressure h C) ork at constant volume w D) ost stable form m E) one of these n 2) Many people believe that coffee 2) _______ may be cooled by placing a silver spoon in the coffee. If 250 ml of coffee at had a spoon at 70 °F placed in it, what would be the final Celsius temperature of the spoon and coffee, assuming that no heat is lost to the surroundings? (Hint: the heat lost by the coffee is equal to the heat gained by the spoon.) The mass of the spoon is 35 g. A) 7.2 °C 5 B) 2.0 °C 8 C) 2.2 °C 7 D) 2.7 °C 9 E) 99 °C 1 3) 100.0 g of nickel at 150 °C was placed in 1.00 L of water at 25.0 °C. The final temperature of the nickel-water mixture was . What is the specific heat of the nickel? A) .130 0 B) .144 0 C) .439 0 D) .28 2 E) .554 0 4) Two solutions, 50.0 mL of 1.00 M BaCl2(aq) and 50.0 mL of 1.00 M Na2SO4(aq), both initially at 21.5 oC, are added to a calorimeter with a heat capacity of 1.10 kJ/oC and the temperature rises to 22.7 oC. Determine qrxn per mole of BaSO4(s) formed in the reaction. A) 26.4 kJ/mol + B) 2.64 kL/mol + C) 2.64 kJ/mol D) 26.4 kJ/mol 5) If 356 J of work is done by a system while it loses 289 J of heat, what is the value of A) 645 J B) 67 J + C) 645 J + D) 67 J - 3) _______ 4) _______ E) 134 J + 5) _______ 6) 1674 J of heat are absorbed by 25.0 mL of NaOH (d = 1.10 g/mL, specific heat = 4.10 J/g °C). The temperature of the NaOH goes up how many degrees? A) 8.0 1 B) 7.2 1 C) 4.2 1 D) 4.8 1 E) one of these n 7) Using the heat of combustion of methanol as -726.6 kJ and the following data: C(graph) + 1/2O2 → CO(g) ΔH° = -110.5 kJ C(graph) + O2(g) H2(g) + 1/2O2(g) → CO2(g) → H2O(l) ΔH° = -393.5 kJ ΔH° = -285.8 kJ 6) _______ 7) _______ Determine ΔH° for the following reaction: CO(g) + 2 H2(g) → CH3OH(l) A) 349 kJ B) 157.8 kJ C) 128 kJ D) 57.8 kJ 1 E) 28 kJ 1 8) 2 NOCl(g) → 2 NO(g) + Cl2(g) 2 NO(g) + O2(g) → 2 NO2(g) 2 NO2(g) → N2O4(g) A) 246.65 B) 95.52 + C) 246.65 + D) 95.52 E) one of these n ΔH° = +75.56 kJ ΔH° = -113.05 kJ ΔH° =-58.03 kJ 8) _______ Compute ΔH° of N2O4(g) + Cl2(g) → 2 NOCl(g) + O2(g) in kJ. 9) Determine △Ho for the decomposition of hydrogen peroxide. H2O2(l) → 1/2 O2(g) + H2O(l) Given: H2(g) + O2(g) → H2O2(l) A) 93.89 kJ B) 98.05 kJ C) 93.89 kJ + D) 191.94 kJ 10) What is the final temperature in the bomb calorimeter if 1.785 grams of benzoic acid (HC7H5O2) is combusted in a calorimeter with a heat capacity of 5.02 kJ/°C and initial temperature of 24.62 °C? The heat of combustion of benzoic acid is -26.42 kJ/g. A) 5.23 °C 1 B) 1.04 °C 5 C) 4.01 °C 3 D) 9.88 °C 2 E) 1.23 °C 3 11) Given that ΔH°f [CO(g)] = -110.5 kJ/mol and ΔH°f [COCl2(g)] = -219.1 kJ/mol, what is the enthalpy of reaction for the formation of phosgene, COCl2 from carbon monoxide, CO, and chlorine gas, Cl2(g)? A) 108.6 kJ B) 219.1 kJ C) 110.5 kJ + D) 110.5 kJ E) 329.6 kJ + 12) Determine the enthalpy change in the following equation: 2/3 H2S(g) + O2(g) → 2/3 SO2(g) + 2/3 H2O(l) A) 562 kJ ΔH°f H2O(l) = -285.8 kJ/mol ΔH°f H2S(g) = -20.63 kJ/mol ΔH°f SO2(g) = -296.8 kJ/mol B) 402 kJ C) 75 kJ 3 D) 02 kJ 4 E) 375 kJ H2(g) + 1/2 O2(g) → H2O(l) △Ho = -187.78 kJ △Ho = -285.83 kJ 9) _______ 10) ______ 11) ______ 12) ______ 13) Which of the following does NOT determine the rate of a reaction? A) requency of collisions f B) ctivation energy a C) alue of ΔH° v D) emperature of reactants t E) one of these n 13) ______ 14) Choose the INCORRECT statement. A) reaction intermediates have fully formed bonds. A B) he rate-determining step is the slow-step. T C) reaction intermediate is produced and used up during the reaction. A D) n activated complex has partially formed bonds. A E) transition state and a reaction intermediate are the same. A 15) What is the rate law for the following mechanism? CH3COOC2H5 + H2O → CH3COOC2H6+ + OH- (S) CH3COOC2H6+ → CH3COOH + C2H5+ (F) C2H5+ + OH- → C2H5OH A) ate = k[CH3COOC2H5][H2O] R B) ate = k[C2H5OH] R C) Rate = k[CH3COOC2H5][H2O]2 D) ate = k[CH3COOH] R E) ate = k[CH3COOC2H5] R 16) For the reaction: 2N2O5(g) → 4NO2(g) + O2(g) the rate law is: (F) Δ[O2 ] = k[N2O5] Δt At 300 K, the half-life is 2.50 × 104 seconds and the activation energy is 103.3 kJ/mol O2. What is the halflife at 350 K? A) 7.3 s 6 B) .145 s 0 C) 2.48 × 104 s D) 1.09 × 10-17 s E) × 106 s 9.3 17) Given the following initial rate data, write the rate law expression. 1 2 3 4 5 A) [A]2 [B] k B) [A] [B] k C) [A]2 k D) [B]2 k E) [A]2 [B]2 k 5.1 × 10-4 5.1 × 10-4 5.1 × 10-4 1.0 × 10-3 1.5 × 10-3 0.35 × 10-4 0.70 × 10-4 0.18 × 10-4 0.35 × 10-4 0.35 × 10-4 3.4 × 10-8 6.8 × 10-8 1.7 × 10-8 6.8 × 10-8 10.2 × 10-8 18) In the first order, reaction A → products, [A] = 0.400 M initially and 0.250 M after 15.0 min, at what time will [A] = 0.200 M? A) 3.9 min 6 B) 5.0 min 1 C) .62 min 9 D) 1.0 min 5 E) 2.1 min 2 19) The reaction A + B → C + D is second order in A and zero order in B. The value of k is 0.012 M-1 min-1. What is the rate of this reaction when [A] = 0.125 M and [B] = 0.435 M? A) × 10-3 M min-1 1.5 B) × 10-3 M min-1 3.4 C) × 10-4 M min-1 1.9 D) × 10-4 M min-1 5 E) M min-1 1.3 20) In a second order reaction: I) the sum of the exponents in the rate law is equal to two. II) at least one of the exponents in the rate law is a two. III) the half-life is not constant. IV) the half-life is constant. V) k can be expressed as M-2s-1 or M-2min-1. A) and III I B) I and IV I C) I and III I D) and IV I E) I, III, and V ...
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This note was uploaded on 04/20/2011 for the course CHEM 120 taught by Professor Barret during the Fall '08 term at McGill.

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