CHE 113 FINAL EXAMINATION December 11, 2012

Transcription

1 CHE 113 FINAL EXAMINATION December 11, 2012 University of Kentucky Department of Chemistry READ THESE DIRECTIONS CAREFULLY BEFORE STARTING THE EXAMINATION! It is extremely important that you fill in the answer sheet EXACTLY as indicated, otherwise your answer sheet may not be processed; ALL entries are to be made on SIDE 1 of the answer sheet. Use a #2 pencil (or softer); fill in the circles completely and firmly. Erasures must be complete. Use only the following categories: NAME: STUDENT NUMBER: TEST FORM: SPECIAL CODES: Print your name starting at the first space, LAST NAME first, then a space, followed by your FIRST NAME, then another space, followed by your MIDDLE INITIAL. Fill in the correct circles below your printed name corresponding to the letters of your name; for the spaces, fill in the top blank circle. This is VERY IMPORTANT! Under IDENTIFICATION NUMBER, put in your 8 DIGIT STUDENT ID NUMBER (do not use the 9 at the beginning of your number) beginning in column A and continuing through column H, column I will be blank, (do NOT use column J at this time); be sure to fill in the correct circles (a common error to be avoided is mistaking "0" for "1"). Fill in the "2" blank in the J column under IDENTIFICATION NUMBER (to indicate Hour Examination II). Use for course and section number; in positions K-P write in your course and section: Dr. April French 113-xxx SIGNATURE: You MUST sign the examination answer sheet (bubble sheet) on the line directly above your printed name. Use your legal signature. Answering Questions: Starting with answer "1" on SIDE 1, fill in the circle indicating the one best answer for each of the 35 questions in this examination. Your score is the sum of the appropriate credit for each response. Grading and Reporting: The examination scores will be posted in Blackboard as soon as possible after the examination. If an error has occurred in scoring your answers, inform your instructor within 48 hours of the posting of your score. BE SURE THAT YOUR TEST HAS 35 QUESTIONS, A PERIODIC TABLE, AND ONE SHEET OF SCRATCH PAPER. You may NOT use your own scratch paper during this examination. Cell phones, computer, and pagers are to be turned off and out of sight during the exam. All exam paper, scratch paper, and scantrons must be handed in at the end of the exam. You may not take any exam materials away from the exam room.

2 Questions 1 15 cover Midterm Exam material 1. Which of the following is considered proper footwear in the lab? A. sandals that allow proper ventilation to the feet B. a comfortable pair of slippers C. closed-toe shoes D. shoes with a high heel and straps 2. For your safety, what should you do prior to leaving the lab? A. wash your hands and any other area of skin that has contacted lab equipment or lab benches. B. get the TA s initial on your lab notebook. C. see that all equipment in the shared drawer is complete and well organized. D. pour all reagents down the drain. 3. Concentrated hydrochloric acid is about 12.1 M. What volume of concentrated HCl is required to produce 5500 ml of M HCl? A. 980 ml C L B ml D L 4. Consider the following reaction: Zn + 2 HCl ZnCl 2 + H 2 What mass of ZnCl 2 can be prepared from the reaction of 1.69 grams of zinc with 1.10 grams of HCl? A g B g C g D g

3 Absorbance 5. The following standard curve was produced by measuring the absorbance of solutions with varying concentrations, following Beer s law Beer's Law Standard Curve y = x R² = Concentration (M) What is the concentration of a solution whose absorbance is 0.436? A M C M B M D M 6. What is the empirical formula of a compound containing 36.5% sodium, 25.4% sulfur, and 38.1% oxygen? A. Na 2 SO 4 C. NaSO 4 B. Na 2 SO 3 D. Na(SO 4 ) 2

4 7. The carbon atom in CSe 2 will have lone pair(s) and a molecular geometry. A. 0, linear C. 4, bent B. 2, bent D. 4, linear 8. How many electron groups are present on the tellurium atom of TeBr 4? A. 6 B. 3 C. 4 D The freezing point of ethanol (C 2 H 5 OH) is C. The molal freezing point depression constant for ethanol is 2.00 C/m. What is the freezing point ( C) of a solution prepared by dissolving 50.0 g of glycerin (C 3 H 8 O 3, a nonelectrolyte) in g of ethanol? A. 115 C C. 109 C B. 120 C D C

5 Temperature (ºC) Temperature (ºC) 10. In lab, a student prepared a solution containing g of sugar (C 6 H 12 O 6 ) in ml of water. The student then conducted a freezing-point depression experiment and obtained the following graphical data: Freezing Point Curve for Pure Water Time (sec) Freezing Point Curve for Sugar Solution Time (sec) What is the freezing point depression constant, K f, for water based upon the data the student collected? A ºC/m C ºC/m B ºC/m D ºC/m

6 11. What is the concentration of urea (MW = 60.0 g/mol) in a solution prepared by dissolving 16 g of urea in 39 g of H 2 O? A. 96 m C m B m D. 6.8 m 12. Consider the following rate data for the reaction below: 2HgCl 2 (aq) + C 2 O 4 2 (aq) 2 Cl (aq) + 2CO 2 (g) + Hg 2 Cl 2 (s) Trial [HgCl 2 ] [C 2 O 2 4 ] Rate, M/s What is the rate constant, k, for this reaction? A M 2 s 1 C M 2 s 1 B M 2 s 1 D M 2 s 1

7 Pressure (torr) 13. In order to determine the rate law for the decomposition of hydrogen peroxide, a student collected pressure versus time measurements as the hydrogen peroxide decomposed with the addition of KI. The following graph was produced at 20 ºC Pressure vs. Time y = x R² = Time (s) Based upon the student s data, what is the initial rate of the reaction in? A C B D According Le Châtelier s principle, which chemical system shifts to the right when pressure is increased? A. CO 2 (g) + H 2 (g) CO(g) + H 2 O(g) B. H 2 (g) + I 2 (g) 2HI(g) C. N 2 (g) + 3H 2 (g) 2NH 3 (g) D. PCl 5 (g) PCl 3 (g) + Cl 2 (g)

8 15. Consider the following chemical reaction: H 2 (g) + I 2 (g) 2HI (g) At equilibrium in a particular experiment, the concentrations of H 2, I 2, and HI were 0.15 M, M, and 0.55 M, respectively. What is the value of the equilibrium constant, K eq, for this reaction? A. 61 C. 23 B D. 111 Questions cover material after the Midterm Exam 16. When is the endpoint of an acid/base titration reached? A. When the indicator changes color. B. When you get tired of filling the buret. C. When a buffer is formed in the solution. D. When an excess of the titrant has been added to the solution being titrated. 17. A student titrated a solution of acetic acid four times and determined the following concentrations for the solution: M, M, M, and M. What is the standard deviation amongst her concentrations? A. ± C. ± B. ± D. ± 0.01

9 ph ph 18. A solution of sodium hydroxide was standardized using g of KHP (KHC 8 H 4 O 4 ) and the following titration data was collected Standardization of NaOH using KHP Volume NaOH (ml) The sodium hydroxide solution was then used to titrate a 22.6 ml of acetic acid of unknown concentration and the following titration curve was produced Titration of Acetic Acid using NaOH Volume NaOH (ml) What is the concentration of the acetic acid? A M C M B M D M

10 19. A 25.0 ml solution of ascorbic acid (H 2 C 6 H 6 O 6 ) was titrated to the second equivalence point using ml of M sodium hydroxide. What is the concentration of the ascorbic acid? A M C M B M D M 20. Which acid-base titration would yield a titration curve of the general form shown? A. NaPO 4 titrated with HCl C. H 3 PO 4 titrated with NaOH B. H 2 CO 3 titrated with NaOH D. NaOH titrated with H 3 PO What is the ph of a 2.36 M solution of acetic acid, CH 3 COOH? The K a for acetic acid is A B C D. 2.19

11 22. A buffer is made by dissolving 0.35 moles of acetic acid in 0.98 moles of sodium acetate in enough water to form 1.00 L of solution. The K a for CH 3 COOH is When NaOH is added to the original buffer solution, the ph slightly, the concentration of CH 3 COOH, and the concentration of CH 3 COO. A. increases, decreases, increases C. decreases, increases, increases B. increases, increases, increases D. decreases, increases, decreases 23. Given the following information regarding the dissociation of phosphoric acid, which would be the most useful in creating a buffer system with a ph of 7.5? H 3 PO 4 - H 2 PO 4 HPO 4-2 H H 2 PO 4 H HPO 4 H PO 4 K 1 = K 2 = K 3 = A. H 3 PO 4 and H 2 PO 4 1 C. HPO 4 2 and PO 4 3 B. H 2 PO 4 1 and HPO 4 2 D. H 3 PO 4 and PO A buffer is prepared from lactic acid (HLac, K a = ) and sodium lactate (Lac ) such that [HLac] = [ Lac ] = 0.05 M. What is the ph of this buffer solution? A B C D What is the ph of a solution in which you dissolve 5.00 g of NaOH in 250 ml of water? Assume no change in volume upon addition of the salt. A C B D. 12.6

12 26. What is the solubility product constant, Ksp, for a M solution of calcium hydroxide? A C B D A student determined the Ksp of manganese(ii) hydroxide to be A reference source lists the Ksp as What is the percent error? A. 98% B. 7.8% C. 54% D. 21% 28. Which of the following best represents the Ksp expression for the dissociation of aluminum sulfate? A. Ksp = [Al +3 ] 2 [SO 4 2 ] 3 C. Ksp = [Al] [SO 4 ] B. Ksp = [Al +3 ] [SO 4 2 ] D. Ksp = [Al +3 ] 3 [SO 4 2 ] What is the molar solubility of the salt AgBr? The solubility product constant, Ksp = A M C M B M D M

13 30. Which of the following is most soluble in water at 25 C? A. Co(OH) 2, Ksp = B. MgF 2, Ksp = C. BaF 2, Ksp = D. Ag 2 SO 4, Ksp = An aqueous solution of Ba(OH) 2 is often used as a reagent in chemistry lab. What is the molar solubility? The solubility product constant, Ksp, of Ba(OH) 2 in water is A M C M B M D M 32. Which of the following best represents the reaction that occurs for a positive sodium hydroxide test? A. 2NaOH (aq) + MgSO 4 (aq) Mg(OH) 2 (s) + Na 2 SO 4 (aq) B. 2NaOH (aq) + MgSO 4 (s) Mg(OH) 2 (aq) + Na 2 SO 4 (aq) C. NaOH (aq) + MgSO 4 (aq) MgOH(s) + NaSO 4 (aq) D. NaOH (aq) + MgSO 4 (aq) Mg(OH) 2 (s) + NaSO 4 (s) 33. Various qualitative tests were performed on an unknown sample and the following results were obtained: 1. The unknown was soluble in water. 2. It had a ph ranging from It bubbled when mixed with vinegar Based on this information, what is the identity of the unknown? A. sucrose C. sodium carbonate B. sodium hydroxide D. magnesium sulfate

14 34. Various qualitative tests were performed on an unknown sample and the following results were obtained: 1. The unknown was soluble in water. 2. It had a ph ranging from It was soluble in 2 M NaOH. 4. Turned green with a flame test. Based on this information, what is the identity of the unknown? A. sodium chloride B. boric acid C. sucrose D. calcium sulfate 35. Which of the following would result in a positive vinegar test? A. calcium carbonate C. potassium bitartrate B. calcium sulfate D. sodium borate

15 FA 2012 CHE 113 Final Exam Key C A D B A B A D B A D D B C A D B C C C D B B C C A D A B C D A C B A