# 1 100 kj 2 100 kj correct 3 550 kj version 173 exam 4

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1. - 100 kJ 2. 100 kJ correct 3. 550 kJ

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Version 173 – Exam 4 302 – sutcliffe – (51060) 6 4. 200 kJ 5. 450 kJ Explanation: The minimum energy required by A to react is represented by the height from A to the peak. 019 10.0 points In this question, n=8. This is because C starts as CH 4 and becomes CO 2 . If the standard free energy change for com- bustion of 1 mole of CH 4 (g) is - 818 kJ · mol 1 , calculate the standard voltage that could be obtained from a fuel cell using this reaction. 1. + 4.24 V 2. - 1.06 V 3. + 8.48 V 4. + 0.53 V 5. + 1.06 V correct Explanation: 020 10.0 points Catalysts work by 1. increasing the exothermicity of the reac- tion, which increases entropy in the surround- ings, making the reaction more favorable. 2. increasing the diffusion rates (collision rate) of molecules in solution. 3. increasing the kinetic energy of the reac- tant molecules. 4. creating a new reaction path with a lower activation barrier. correct Explanation: Definition 021 10.0 points This is a BONUS question: get it correct your max points are 250/240; get it wrong and your max points are 240/240. The overall reaction for the discharge of a nickel/cadmium cell is Cd + NiO 2 + 2 H 2 O Cd(OH) 2 + Ni(OH) 2 Which of the following statements is true? 1. Cadmium metal loses 2 electrons and is converted to Cd 2+ at the cathode. 2. It is impossible to recharge a nickel/cadmium cell. 3. The nickel is oxidized during this reac- tion. 4. Insoluble Cd(OH) 2 is deposited on the anode. correct Explanation: Looking at the reaction above, Cd Cd 2+ + 2 e is an oxidation reaction that will occur at the anode. The nickel is not oxidized because we have shown that Cd is being oxidized. Nickel/cadmium batteries are rechargable. Insoluble CD(OH) 2 is deposited on the an- ode since Cd is oxidized at the anode. 022 10.0 points A certain reaction is found to have a rate constant of 1.50 × 10 8 sec 1 at 0 C and an activation energy of 45.0 kJ · mol 1 . What will be its rate constant at 100 C? 1. k = 68 . 4 s 1 2. None of the other answers is correct. 3. k = 7 . 37 × 10 11 s 1 4. k = 3 . 05 × 10 6 s 1 correct 5. k = 3 . 10 × 10 3 s 1 Explanation:
Version 173 – Exam 4 302 – sutcliffe – (51060) 7 T 1 = 273 K T 2 = 373 K E A = 45 . 0 kJ k 1 = 1 . 50 × 10 8 sec 1 ln k 2 k 1 = ln k 2 - ln k 1 = E A R parenleftbigg 1 T 1 - 1 T 2 parenrightbigg ln k 2 = ln k 1 + E A R parenleftbigg 1 T 1 - 1 T 2 parenrightbigg = ln 1 . 50 × 10 8 + 45000 8 . 314 parenleftbigg 1 273 - 1 373 parenrightbigg = - 12 . 699876 k 2 = 3 . 05 × 10 6 s 1 023 10.0 points Note: use a = 1 in this question. For the reaction cyclopropane propene a plot of ln[cyclopropane] vs time in seconds gives a straight line with slope - 4 . 1 × 10 3 s 1 at 550 C. What is the rate constant for this reaction?
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