CHM 131 - Final - 2004

CHM 131 - Final - 2004 - ROCHESTER 18 December 2004...

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Chemistry 131 – Final Exam 18 December 2004 8:30 a.m. to 11:30 a.m. Name: ________________________ ID #: ________________________ This exam consists of ten (10) questions, one extra credit problem, and 2 pages of potentially useful information. Please check BEFORE you begin to make sure that you have a complete exam. Please do all your work on the pages provided. You may use the backside of pages for additional work, but please tell us that you are doing so (i.e. an arrow with a note in clear English saying "more work on back"). SHOW ALL WORK . GIVE UNITS for all answers that require them. Partial credit can only be given for those answers for which work is provided. CIRCLE YOUR ANSWER. We ask this so that we don't have to interpret what you intended as your final answer. If you make any 5% approximations you will not receive credit if the approximation is not valid. Also if you need to use the quadratic formula, you need to SET UP THE CALCULATION and INSERT THE RELEVANT NUMBERS INTO THE FORMULA . Credit will not be given for answers that appear out of nowhere due to a fancy calculator. Assume all gases are ideal. GOOD LUCK and HAPPY HOLIDAYS! Prob. 1(30) 2(25) 3(25) 4(30) 5(25) 6(35) Score Prob. 7(30) 8(30) 9(30) 10(40) E.C.(5) Total (300) Score U N I V E R S I T Y O F University of Rochester R h t N Y k 14627 0216 COLLEGE OF ARTS AND SCIENCE DEPARTMENT OF CHEMISTRY ROCHESTER
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1 ) The following calculations can be done either without a calculator or with minimal work and you do NOT need to show calculations. For the following problems assume that the weak acid HA has a K a = 1.0 x 10 -5 . (4 pts each) a) Find the pH of a solution of 0.2 M HA and 0.2 M NaA: pH = ______. b) You mix 40.0 g NaOH (m.w. = 40.0) with enough H 2 O to make a 1.00 L solution: pH = ______. c) You mix 4.0 g NaOH (m.w. = 40.0) with 1.00 L of a 0.2 M HA solution: pH = ______. d) You mix 4.0 g NaOH (m.w. = 40.0) with 1.00 L of a 0.2 M HNO 3 solution: pH = ______. e) Consider a solution of 2.0 M HNO 2 and 1.0 M NaNO 2 Circle the correct answer. The solution is not a buffer pH < 7.00. [OH - ] > [H + ] (1), (2) and (3) are false f) Consider a solution of 2.0 M CH 3 NH 2 and 1.0 M CH 3 NH 3 Cl. Circle the correct answer. The solution is not a buffer pH < 7.00. [OH - ] > [H + ] (1), (2) and (3) are false g) (3 pts) Ignoring any weak acid-base equilibrium processes , which saturated solution has the highest concentration of sulfide ions? Iron Sulfide Zinc Sulfide Lead Sulfide Nickel Sulfide All the same h) (3 pts) Ignoring any weak acid-base equilibrium processes , which solution has the highest concentration of total ions? Sodium Chloride Sodium Nitrate Sodium Sulfide All the same
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2 The chemical equation describing the dissolution of PbCl 2 in water is given by: PbCl 2 ( s ) ! Pb 2+ ( aq ) + 2 Cl - ( aq ) a) (4 pts) What is the expression for K sp for this reaction (i.e. law of mass action)? b) (6 pts) Calculate the K sp value for PbCl 2 , which has a solubility of 0.0159 mol/L at 300 K.
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CHM 131 - Final - 2004 - ROCHESTER 18 December 2004...

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