Chem1C_FinalHan08_FormB_solution

Chem1C_FinalHan08_FormB_solution - Chem. 1C Final June, 12,...

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Chem. 1C Final FORM B First letter of your last name: June, 12, 2008 Name: Last Name First Name Perm # INSTRUCTIONS: No hats allowed. No sharing of calculators. Cell Phones, iPods, headsets, etc. must be turned off and put away. SCANTRON FORM: Use a PENCIL 1) Write your name 2) Bubble in FORM B 3) Bubble in your PERM number (7 digits only, no extra numbers) There are 8 pages including 1 page of info sheet and 33 questions. All questions are worth 5 points. One question is not a multiple choice. For this, SHOW ALL YOUR WORK on the exam. Turn in the Scantron form and your Exam upon I.D. check. 1. Each atom in HF has a fractional charge of 0.416. What is the dipole moment of HF? (Info: the distance between H and F atoms is 9.17 · 10 -11 m and the charge of one electron is 1.60 · 10 -19 C) (a) 1.83 D (b) 2.53 D (c) 6.10 D (d) 1.47 D (e) 4.40 D 2. Which of the following molecules has a dipole moment? (a) PH 3 (b) SO 3 (c) BF 3 (d) NO 3 - (e) CO 2 3. Of the ions below, which ion has the smallest atomic radius? (a) Te 2- (b) Cs + (c) La 3+ (d) Ba 2+ (e) I - Source: Q 13.17 4. Use the bond energy values listed in the table on the next page to estimate ΔH for the combustion reaction of ethanol. (Hint: combustion is when ethanol reacts with oxygen under high temperature. Consider the bonds that are formed and bonds that are broken to solve this question. Also, keep in mind that the average bond energy for the C=O bond in carbon dioxide is 799 kJ/mol as indicated on the table with *.) (a) +1280 kJ (b) 1280 kJ (c) +1163 kJ (d) –1163kJ (e) –164.5 kJ Source: Q 13.34
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5. Which of the following descriptions is incorrect? (a) Resonance occurs when more than one valid Lewis structure can be written for a particular molecule in which the atoms and bonds undergo rearrangement from one structure to another. (b) There is a close relationship between the strength of the covalent bond energies and the chemical reactivity of that bond. (c) A triple bond shows higher reactivity and has shorter bond length compared to a single bond. (d) Lone pair electrons are localized on a particular atom while bonding electrons are localized between atoms. (e) Any compound that conducts an electric current when melted will be classified as ionic, and is referred to as a “salt”. Word for word in lecture notes. 6. When you use the idea of hyperconjugation to describe the electron distribution in SF 6 , what is the formal charge on the sulfur atom? (a) +2 (b) +1 (c) 0 (d) –1 (e) –2 Exact example of lecture note. 7. Write down the most likely Lewis structure of SO 4 -2 . Base your decision on minimizing the formal charge. Note that more electronegative oxygen must have a more negative formal charge than sulfur. Show your answer on your exam only!
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Chem1C_FinalHan08_FormB_solution - Chem. 1C Final June, 12,...

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