Chem II Spring 2008 Final

Sample Exam #2 1. Given the equation: H 2 PO 4 - + HCO 3 - ? HPO 4 -2 + H 2 CO 3 , which statement is TRUE? a. HCO 3 - is an acid and H 2 CO 3 is its conjugate base b. H 2 PO 4 - is acting as both an acid and a base c. H 2 PO 4 - is an acid and HPO 4 -2 is its conjugate base d. HCO 3 - is a base and HPO 4 -2 is its conjugate e. H 2 PO 4 - is an acid and H 2 CO 3 is its conjugate 2. In the following two reversible acid-base reactions, which sides are favored? I. HF + NH 3 ? NH 4 + + F - II. HSO 4 - + F - ? HF + SO 4 -2 a. the products in both b. the reactants in both c. the products in I and the reactants in II d. the reactants in I and the products in II e. cannot predict either one 3. Which species below could be amphoteric? a. HSO 4 - b. H 3 O + c. H 3 PO 4 d. H 2 O e. both a and d 4. Which of the following pairs of acids is incorrectly ordered (stronger to weaker)? a. HCl > HF b. HClO > HBrO c. HBrO 3 > HBrO d. HIO 4 > HClO 4 e. both b and c are incorrect 5. A 0.10M aqueous solution of a weak acid HA has a measured pH of 5.00. What is the value of K a for this weak acid? a. 1.0 x 10 -9 b. 1.0 x 10 -5 c. 1.0 x 10 -6 d. 1.0 x 10 -1 e. 1.0 x 10 -11 6. What is the pH of a 0.010 M solution HBrO, which has a K a = 2.5 x 10 -9 ? a. 5.30 b. 8.70 c. 8.60 d. 5.40 e. 3.70 7. The pH of a 0.015 M NH 3 solution is 10.72. What is its OH - concentration? a. 1.90 x 10 -11 M b. 5.25 x 10 -4 M c. 1.91 x 10 3 M d. 5.16 x 10 -1 M e. need to know the value of K b 8. When each is dissolved in water, which of the following salts will form an acidic solution? a. Fe(NO 3 ) 3 b. NaClO c. CH 3 NH 3 Cl d. both a and c e. none of these 9. What is the pH for a buffer that has 0.10M CH 3 NH 2 and 0.050M CH 3 NH 3 Cl? K b for CH 3 NH 2 = 4.4 x 10 -4 . a. 10.34 b. 3.64 c. 10.94 d. 3.04 e. 10.64 10. A solution of HF is partially titrated by adding 250mL of a 0.10M NaOH solution to 750mL of a 0.10M HF solution. If K a for HF is 6.8 x 10 -4 , then what is the resulting pH? a. 3.17 b. 3.65 c. 2.69 d. 3.47 e. none of the above 11. To 100mL a buffer solution that is 0.10M in both HCHO 2 and NaCHO 2 , we add 0.0020 moles of HCl. What will be the pH of the buffer after the addition of the strong acid? Assume that the volume change is negligible and K a for HCHO 2 is 1.7 x 10 -4 . a. 3.77 b. 3.17 c. 3.59 d. 1.70 e. none of the above 12. A solution that is made by combining 400.mL of 0.20M HCl with 600.mL of 0.10 M NaOH will have a pH of a. 1.1 b. 1.7 c. 2.0 d. 7.0 e. 12.3 13. If you mix 0.10 mol of NaOH with 0.10 mol of HC 2 H 3 O 2 in 1.0 L of water, you will have a solution that is a. neutral, pH = 7 b. slightly acidic, pH between 2 and 7 c. slightly basic, pH between 7 and 12 d. very acidic, pH less than 2 e. very basic, pH greater than 12 14. The molar solubility for PbF 2 is 2.1 x 10 -3 M. Calculate the value of K sp for PbF 2 . a. 4.4 x 10 -6 b. 4.2 x 10 -7 c. 9.3 x 10 -7 d. 3.7 x 10 -8 e. 9.3 x 10 -9 15. What is the concentration of Ag + in a saturated solution of Ag 3 PO 4 ? The K sp for this compound is 1.8 x 10 -18 . a. 1.6 x 10 -5 M b. 4.8 x 10 -5 M c. 1.3 x 10 -9 M d. 2.0 x 10 -3 M e. 3.7 x 10 -5 M 16. The K sp for AgI is 1.0 x 10 -16 . If you mix 500.mL of 1 x 10 -8 M Ag + with 500.mL of 1 x 10 -8 M I - , then a. AgI will precipitate b. no precipitate forms as Q is less than K c. 1 x 10 -8 moles of AgI will form d. a saturated solution will form as Q = K e. a and c are true 17. What is the minimum concentration of F - ion required to cause PbF 2 to precipitate from a 0.010 M Pb(NO 3 ) 2 solution? The K sp for PbF 2 is 2.7 x 10 -8 . a. 5.4 x 10 -6 M b. 2.7 x 10 -6 M c. 1.6 x 10 -3 M d. 1.4 x 10 -6 M e. 8.2 x 10 -4 M 18. What is the concentration of the Cd +2 ion in a solution that is 0.010M Cd(NO 3 ) 2 and 1.0M NH 3 ? K f for Cd(NH 3 ) 4 +2 is 1.0 x 10 7 . a. 5.6 x 10 -3 M b. 1.2 x 10 -9 M c. 7.2 x 10 -12 M d. 1.0 x 10 -2 M e. 1.0 x 10 -5 M Answer Key: 1C, 2A, 3E, 4D, 5A, 6A, 7B, 8D, 9C, 10E (pH = 2.87), 11C, 12B, 13C, 14D, 15B, 16B, 17C, 18B R. John Muench Sample Exam #2