Practice_Final_Exam_A.pdf - PRACTICE FINAL EXAMINATION A...

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PRACTICE FINAL EXAMINATION A CHEMISTRY S-1 You should give yourself 3 hours to complete this exam NAME: ____________________________________________ SECTION TF: ________________________________________ NOTES: 1. This exam has 9 pages with 9 problems, plus the cover sheet and scrap paper. Please do not separate any sheets of the exam. A separate sheet with the Useful Information, a Periodic Table, and a Titration Curve will be distributed; this sheet will be collected but nothing on it will be graded. 2. Note the point values of each exam question, and consider where you can best spend your time. 3. Answer all questions on the exam sheets. Put your final answers in the boxes provided . If you must use the back or the scrap paper, then please indicate that clearly! 4. Do not use red pen! 5. For full credit, show all calculations ; this also helps us award partial credit. 6. All numerical answers must include correct units for full credit. 7. For all problems, the temperature is 25°C unless noted otherwise. 1. ____________ / 16 2. ____________ / 18 3. ____________ / 16 4. ____________ / 16 5. ____________ / 16 6. ____________ / 18 7. ____________ / 16 8. ____________ / 18 9. ____________ / 16 TOTAL: ___________ / 150 Congratulations on completing Chem S-1!
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1 1 ( ______ / 16 pts) 1. Compound X contains only the elements C, H, and O. a) When 5.00 grams of Compound X are completely combusted in excess oxygen, 12.22 g of CO 2 and 3.57 g of H 2 O are collected. Determine the empirical formula of Compound X. (8 pts) empirical formula: b) The molecular formula of Compound X is the same as its empirical formula. Write a balanced chemical reaction for the complete combustion of liquid Compound X in excess oxygen. (Please include state symbols such as ( s ), ( aq ), etc.) (2 pts) c) A bomb calorimeter is filled with 0.050 moles of Compound X and excess oxygen gas at an initial temperature of 25.0°C. A spark ignites the mixture, Compound X burns completely, and the temperature of the calorimeter rises to 35.8°C. The total heat capacity of the calorimeter and its contents is 18.2 kJ/°C. Calculate the heat of combustion ( ! comb ) of Compound X in units of kJ/mol. (6 pts) ! comb = kJ/mol
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2 2 ( ______ / 18 pts) 2. Consider atomic bromine, Br, and molecular bromine, Br 2 . a) Write the electron configuration of Br. Use the noble gas abbreviation. (2 pts) Br : b) Atomic bromine is: (circle) paramagnetic diamagnetic (1 pt) c) What are the n and l quantum numbers of the outermost electron in Br? (2 pts) n = l = d) Valence molecular orbital electron configurations for 4th period diatomic molecules can be written in a similar fashion as those for 2nd period diatomic molecules. Write the valence molecular orbital electron configuration for the Br 2 molecule. (We are looking for something analogous to ( ! 2s ) 2 ( ! * 2s ) 2 etc. . . ). (3 pts) Br 2 : e) The bond enthalpy of the Br–Br bond in Br 2 is 193 kJ/mol. What is the longest wavelength of light that could break the Br–Br bond in a gaseous Br 2 molecule? (4 pts) " = f) Bromine-80 is a radioactive isotope of bromine that undergoes beta decay with a half-life of 17.7 minutes. How long will it take for 1.50 grams of bromine-80 to decay from an initial 4.00-gram sample? (4 pts) time = g) Consider the atomic radius of bromine and several other elements in Periods 3 and 4.
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