Final Exam

# Final Exam - Version 243 – Final – Sutcliffe –(53120...

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Unformatted text preview: Version 243 – Final – Sutcliffe – (53120) 1 This print-out should have 45 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Gallium, with a mass of 69.72, has 2 isotopes. One isotope ( 69 31 Ga ) has a natural abundance of 60.5%. What is the mass of the other isotope of Gallium? 1. 71. correct 2. 69. 3. 68. 4. 70. 5. 31. Explanation: 002 10.0 points For the vaporization of ethanol, Δ H vap = 38 . 56 kJ/mol and Δ S vap = 109 . 7 J/mol · K. What is the boiling point of ethanol? 1. 2.84 K 2. 351.5 K correct 3. 0.352 K 4. 2842 K 5. 273.502 K Explanation: Δ S vap = q T = Δ H vap BP so BP = Δ H vap Δ S vap = 38 . 56 × 10 3 J / mol 109 . 7 J / mol · K = 351 . 504 K 003 10.0 points LP gas (liquid propane, C 3 H 8 ) is the fuel used in gas grills as well as a main source of heat energy for many rural residences. What is the mass of 5 . 83 × 10 17 molecules of liquid propane? 1. 6 . 00 × 10 − 17 g 2. 2 . 57 × 10 19 g 3. 4 . 27 × 10 − 5 g correct 4. 6 . 89 × 10 − 7 g 5. None of these 6. 6 . 41 × 10 18 g 7. 1 . 99 × 10 23 g 8. 3 . 42 × 10 7 g Explanation: MW propane = 3(12 . 011 g / mol) +8(1 . 0079 g / mol) = 44 . 0962 g / mol 5 . 83 × 10 17 molec propane × 1 mol propane 6 . 02 × 10 23 molec propane × 44 . 0962 g propane 1 mol propane = 4 . 27045 × 10 − 5 g propane 004 10.0 points Select the appropriate coefficient for O 2 when the equation ? O 2 (g) +? C 5 H 12 (g) → ? CO 2 (g) +? H 2 O(g) is balanced using the smallest possible inte- gers. 1. 3 2. 2 Version 243 – Final – Sutcliffe – (53120) 2 3. 8 correct 4. 5 5. 4 Explanation: A balanced equation must have the same number of each kind of atom on both sides of the equation. We find the number of each kind of atom using equation coefficients and composition stoichiometry. For example, we find there are 12 H atoms on the product side: ? H atoms = 4 H 2 O × 2 H 1 H 2 O = 12 H The balanced equation is C 5 H 12 + 8 O 2 → 5 CO 2 + 6 H 2 O and has 5 C, 12 H, and 16 O atoms on each side. The coefficient of O 2 is 8. 005 10.0 points A reaction for which Δ S and Δ H are negative can become spontaneous as the temperature 1. remains the same. 2. increases. 3. decreases. correct Explanation: Δ H = (- ) , Δ S = (- ) Δ G = Δ H- T Δ S Δ G = (- )- T (- ) = (- ) + T For spontaneous processes, Δ G must be negative. This will only happen if T is below a certain temperature. 006 10.0 points How many s electrons and p electrons does Mn possess? 1. 7 s , 13 p 2. 8 s , 6 p 3. 8 s , 12 p correct 4. 6 s , 18 p 5. 6 s , 12 p 6. 7 s , 18 p 7. 8 s , 18 p 8. 6 s , 6 p 9. 7 s , 12 p Explanation: The electron configuration for Mn is 1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2 3 d 5 2 + 2 + 2 + 2 = 8 s 6 + 6 = 12 p 007 10.0 points Note one Angstrom is equal to 0.1 nanometer....
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Final Exam - Version 243 – Final – Sutcliffe –(53120...

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