CHM 152/154 HOUR EXAM II Diebolt Summer 2010 pts earned name pts possible multiple choice 52 Parts II and III 73 Total Pts 125 Part One: Multiple choice. Mark the correct answers on the provided scantron form. Make sure to write your name on the information side of the scantron and bubble your 10 digit PHONE # for the ID # on the answer side. (Use the phone # you provided on the first exam.) There are 14 multiple choice questions worth 4 points each (56 points) 1. The concentration of H + for a solution is 1.0 10 9 M. The poh is and the solution would be. A. 9, basic B. 9, acidic C. 5, basic D. 5, acidic E. none of these 2. Select the conjugate acid for (CH 3 ) 2 NH. A. H 3 O + B. (CH 3 ) 2 N C. OH D. (CH 4 ) 2 NH E. (CH 3 ) 2 NH 2 + 3. Select the solution with the highest. A. 0.10 M Ca(OH) 2 B. 0.10 M NH 3 C. 0.10 M H 2 O D. 0.10 M HBr E. 0.10 M KOH 4. Equilibria lies on the reactant side for the following reaction: (aq) + HCN(aq) HCHO2 (aq) + CN (aq) Select the weakest acid and weakest base for this reaction. Acid Base A. HCN CN B. HCN C. H CN D. H 5. Consider the K a values for the following acids: K a = 5.6 x 10 10 HC 2 H 3 O 2 K a = 1.8 x 10 5 H K a = 1.8 x 10 4 HOC 6 H 5 K a = 1.6 x 10 10 HF K a = 7.2 x 10 4 NH 4 + Which of the following is the strongest conjugate base? A. NH 3 B. C 2 H 3 O 2 C. D. OC 6 H 5 E. F 6. One molar solutions of KNO 2, AlBr 3, Ba(ClO 4 ) 2 will result in solutions that are, respectively, A. neutral, acidic, and neutral B. basic, acidic, and neutral C. basic, neutral, and acidic D. neutral, acidic, and basic E. acidic, neutral, and acidic CHM152 Sum 10 Diebolt Exam 2 1
7. When comparing two different 0.10 M acid solutions, which statement is False? A. The stronger acid has a higher percent ionization. B. The stronger acid has a lower reading. C. The stronger acid has a smaller [H 3 O + ]. D. The stronger acid has a higher K a value. E. Both acids require the same volume of NaOH(aq) to be neutralized. 8. Which combination cannot function as a buffer solution? A. HCN and NaCN B. NH 3 and NH 4 Cl C. HF and NaF D. NaOH and NaNO 3 E. HNO 2 and NaNO 2 9. According to the Lewis theory, an acid is A. an electron pair acceptor B. an electron pair donor C. a proton acceptor D. a proton donor E. a hydroxide ion donor 10. When NH 3 (aq) is titrated by a solution of HNO 3 (aq), the at the equivalence point is A. 7 B. less than 7 C. greater than 7 D. can t tell 11. Which plot shows the titration curve expected when HCO 2 H(aq) is titrated by KOH(aq)? A. B. C. D. 12. Consider a buffer solution prepared from HOCl and NaOCl. Which is the net ionic equation for the reaction that occurs when NaOH is added to this buffer? A. OH + OCl HOCl + O 2 B. Na + + HOCl NaCl + OH C. H + + OCl HOCl D. NaOH + HOCl H 2 O + NaCl E. OH + HOCl H 2 O + OCl 13. What change will be caused by the addition of a small amount of NaOH(aq) to a buffer solution containing NH 4 NO 3 (aq) and NH 3 (aq)? a. [H + ] will significantly increase b. [OH ] will significantly increase c. [NH 4 + ] and [NH 3 ] will both increase d. [NH 4 + ] will decrease and [NH 3 ] will increase e. [NH 4 + ] will increase and [NH 3 ] will decrease CHM152 Sum 10 Diebolt Exam 2 2
14. How will the of a HCN(aq) solution change after KCN(aq) is added to it? A. will not change B. will decrease C. will increase D. need more information to tell Part Three. Numerical Problems. Please SHOW YOUR WORK for full credit. Use the correct number of significant figures for your answers and circle your final answer for each problem. (69 pts) 1. Fluoroacetic acid, HCO 2 CH 2 F, is a weak acid found in the poisonous gifblaar plant. a) A 0.0861 M solution of fluoroacetic acid has a of 1.86. Calculate the K a value for HCO 2 CH 2 F. (9 pts) b) Calculate the %ionization for the fluoroacetic acid solution given above. (3 pts) 2. A NaCN solution is prepared in the laboratory. a) Write the hydrolysis reaction that occurs for the NaCN solution. (4 pts) b) Calculate the of a solution that contains 24.8 grams of NaCN in 775 ml of solution. K a for HCN is 4.90 x 10 10. (9 pts) CHM152 Sum 10 Diebolt Exam 2 3
3. Calculate the, poh, and [OH ] for a 4.35x10 3 M HClO 4 (aq) solution. (7 pts) 4. You have 250.0 ml of a buffer solution containing 0.375 M HC 3 H 3 O 2 and 0.310 M KC 3 H 3 O 2. What is the after 50.0 ml of 0.600 M HCl is added to this buffer solution? For HC 3 H 3 O 2, 5.5 10 5. (13 pts) CHM152 Sum 10 Diebolt Exam 2 4
5. A solution of nitric acid, HNO 3, is being titrated with KOH. Calculate the after 22.5 ml of 0.175 M KOH is added to 10.5 ml of 0.250 M HNO 3. (10 pts) 6. A sample of butyric acid, HC 4 H 7 O 2, is titrated with NaOH solution. What is the after 12.5 ml of 0.300 M NaOH has been added to 25.0 ml of 0.150 M HC 4 H 7 O 2? For HC 4 H 7 O 2, K a = 1.5 10 5 (14 pt) CHM152 Sum 10 Diebolt Exam 2 5