Chem 1212K Practice Exam 2 - CHEM 1212K 1. Practice Exam...

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Unformatted text preview: CHEM 1212K 1. Practice Exam Two Spring 2011 Calculate the [H3O+] in a solution that is 0.10 M in NaF and 0.20 in HF. 1. Ka = 7.2 x 10–4 A) 0.20 M B) 7.0 x 10–4 M C) 1.4 x 10–3 M D) 3.5 x 10–4 M E) none of these 2. Y2.2.are given a solution of the weak base Novocain, Nvc, and its conjugate ou acid, NvcH+. Its pH is 11.00. You add more NvcH+ to the solution. Which statement is true? A) The pH and the pOH both increase. B) The pH and the pOH both decrease. C) The pH and the pOH remain unchanged. D) The pH increases and pOH decreases. E) The pH decreases and the pOH increases. 3. What quantity of NaOH(s) must be added to 1.00 L of 0.200 M HCl to achieve a pH of 3. 12.00? (Assume no volume change.) A) 0.200 mole B) 0.420 mole C) 0.210 mole D) 0.010 mole E) none of these 4. For ammonia, Kb is 1.8 x 10-5 . To make a buffered solution with pH 10.0, the ratio of NH4Cl to NH3 must be: A) 1.8 : 1 B) 1 : 1.8 C) 0.18 : 1 D) 1 : 0.18 E) none of these CHEM 1212K 5. Practice Exam Two Spring 2011 The pH of a 0.010 M weak monoprotic acid solution is 5.24. Calculate Ka for this acid. 69. A) 3.3 x 10–9 B) 1.8 x 10–6 C) 4.2 x 10–7 D) 9.6 x 10–8 E) none of these 6. Calculate the [H3O+] in a 0.010 M solution of HCN, Ka = 6.2 x 10–10. A) 1.0 x 10–7 M B) 2.5 x 10–6 M C) 3.6 x 10–3 M D) 6.2 x 10–10 M E) none of these - 7. The pKa of HClO is 7.5. Calculate the pH of a 0.5 M solution of ClO . A) 7.5 B) 6.5 C) 3.9 D) 10.6 E) 0.3 8. The hydrogen sulfate or bisulfate ion HSO4– can act as either an acid or a base in water solution. In which of the following equations does HSO4– act as an acid? A) HSO4– (aq) + H2O(l) → H2SO4 (aq) + OH– (aq) B) HSO4– (aq) + H3O+ (aq) → SO3 (aq) + 2H2O(l) C) HSO4– (aq) + OH– (aq) → H2SO4 (aq) + O2–(aq) D) HSO4– (aq) + H2O(l) → SO42– (aq) + H3O+ (aq) E) none of these CHEM 1212K Practice Exam Two Spring 2011 9. The graph below represents the titration of 100.0 mL of 0.100 M H2SO3 with 0.200 M NaOH. What is the pH at point A on the graph? For H2SO3: Ka1 = 1.4 x 10‐2 Ka2 = 6.5 x 10‐8 A) 1.85 B) 2.15 C) 6.81 D) 7.19 E) 12.15 10. A buffer is composed of 0.200 M acetic acid (HC2H2O3, Ka = 1.8 x 10‐5) and 0.250 M KC2H2O3. What is the pH of the resulting solution after 0.15 mol of KOH are added to 1.00 L of the buffer? Assume that the change in volume is negligible. A) 0.40 B) 0.70 C) 3.84 D) 4.74 E) 5.64 CHEM 1212K Practice Exam Two Spring 2011 11. A 75.0 mL sample of 0.34 M NaOH was titrated with 0.34 M HBr. What is the pH of the solution at the equivalence point? A) 0.47 B) 1.59 C) 7.00 D) 12.41 E) 13.53 12. Which base is strongest? A) (CH3CH2)2NH B) C6H5NH2 C) CH3NH2 D) NH3 E.) C5H5N Kb = 8.60 x 10‐4 Kb = 4.00 x 10‐10 Kb = 4.40 x 10‐4 Kb = 1.76 x 10‐5 Kb = 1.70 x 10‐9
 
 13. What concentration must a solution of HNO2 have in order to have the same pH as a 0.0076 M solution of HClO4? The Ka of HNO2 is 4.6 x 10‐4 and the Ka of HClO4 is 1.0 x 107. A) 0.0076 M B) 0.13 M C) 0.98 M D) 2.1 M E) 7.6 x 10‐10 M 14. Which statement regarding the salt NH4Br is true? Ka HBr = 1.0. x 107 Kb NH3 = 1.76 x 10‐4 Ka NH4+ = 5.68 x 10‐11 A) It is a neutral salt because it is derived from a weak acid and a weak base. B) It is a basic salt because NH3 is a stronger base than Br‐. C) It is a basic salt because the weak conjugate base Br‐ undergoes hydrolysis to produce [OH‐] D) It is an acidic salt because NH4+ undergoes acid hydrolysis to produce [H3O+]. E) It is acidic because NH4+ is a stronger acid than HBr. CHEM 1212K Practice Exam Two Spring 2011 15. The pH of a cup of coffee is 4.7. What is the hydroxide ion concentration? A) 2.0 x 10‐5 B) 5.0 x 10‐10 C) 1.0 x 10‐7 D) 4.7 x 10‐10 E) 6.7 x 10‐1 16. An experiment using the bacteria Bacillus sphearicus must be kept at a pH near 5.25 in order for the bacteria to survive. Which is the best weak acid to use in the buffer? A) HC3H3O3, Ka = 4.1 x 10‐3 B) HC2Cl3O2, Ka = 2.2 x 10‐1 C) HC3H5O2, Ka = 1.3 x 10‐5 D) HClO, Ka = 2.9 x 10‐8 E) HIO, Ka = 2.3 x 10‐11 17. Consider the titration of a 250.0 mL sample of 0.174 M CH3NH2 with 0.150 M HBr. Calculate the pH when the following 290.0 mL of titrant have been added. Kb CH3NH2 = 4.4 x 10‐4 Ka HBr = 1.0 x 107 A) 5.86 B) 1.81 C) 3.37 D) 6.80 E) 3.56 CHEM 1212K Practice Exam Two Spring 2011 18. Which acid is best represented by curve A in the graph? Explain your choice. Ka1 H2SO3 = 1.7 x 10‐2 A) B) C) D) E) Ka HF = 3.5 x 10‐4 Ka = HClO = 2.9 x 10‐8 Ka HCN = 4.9 x 10‐10 HClO4 H2SO3 HF HCN HClO 
 
 19. Which is the correct mathematical expression for the molar solubility (s) in mol/L (S) of Fe3(PO4)2? A) 6S2 B) 12S3 C) 6S5 D) 108S5 E) 5S6 20. Determine the molar solubility of Fe(OH)2 in pure water. Ksp Fe(OH)2 = 4.87 x 10‐17 A) 3.65 x 10‐6 M B) 2.44 x 10‐17 M C) 2.30 x 10‐6 M D) 1.62 x 10‐17 M E) 4.03 x 10‐9 M CHEM 1212K Key 1. C 2. E 3. C 4. C 5. A 6. B 7. D 8. D 9. D 10. E 11. C 12. A 13. B 14. D 15. B 16. C 17. A 18. C 19. D 20. C Practice Exam Two Spring 2011 ...
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This note was uploaded on 08/01/2011 for the course CHEMISTRY 1212 taught by Professor Soper during the Spring '10 term at Georgia Institute of Technology.

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