EXAM PRACTICE QUESTIONS Chapter 19 1. Calculate the [H3O+] of a solution that is 0.100 M in HOCl and 0.0300 M in NaOCl? Answer: 1.17 u 10-8 2. A solution is made by combining 500 mL of 0.10 M HF with 300 mL of 0.15 M NaF. Calculate the pH of the solution Answer: 3.10 3. What is the pH of a solution containing aqueous ammonia and ammonium nitrate in a molar ratio of 5.0 to 3.0? Answer: 9.48 4. Indicate which of the following combinations would produce a buffer. A) HCN and KCN _______________ B) HClO4 and NH4ClO4 _______________ C) NH3 and NH4Br _______________ D) KI and HI _______________ Answer: A) yes B) no C) yes D) no 5. If 0.040 moles of solid NaOH is added to 1.0 L of a solution that is 0.1 M NH3 and 0.20 M NH4Cl, what will be the pH of the resulting solution? Assume no volume change due to the addition of the NaOH. Answer: 9.20 6. What is the pH of a solution that is 0.15 M in HOCl and 0.25 M NaOCl after 0.050 mole of HCl has been bubbled into the solution? Assume no volume change. Answer: 7.46 7. Calculate the mass of solid NaCH3COO that must be added to 1.0 L of 0.20 M CH3COOH solution so that the pH of the resulting solution will be 5.00. Assume no volume change due to addition of solid NaCH3COO. Answer: 30 g 8. It is desired to buffer a solution at pH = 4.30. What molar ratio of CH3COOH to NaCH3COO should be used.Answer: 2.8 9. Calculate the pH for a buffer solution prepared by mixing 100. mL of 0.60 M NH3 and 200. mL 0.45 mL of NH4Cl. Answer: 9.08 10. The nonionized form (HIn) of an acid indicator is yellow, and its anion is blue. The Ka of this indicator is 10-5. What will be the color of the indicator in a solution of pH 3? Answer: yellow 11. What is the pH of the solution resulting from the addition of 30.0 mL of 0.200 M HClO4 to 20.0 mL of 0.150 M NaOH? Answer: 1.22 12. When a weak base is titrated with a strong acid, the pH at the equivalence point is always (< 7, 7, > 7) _______. Answer: < 7 13. What is the pH at the equivalence point in the titration of 50.0 mL of 0.100 M hydrofluoric acid with 0.100 M sodium hydroxide? Answer: 7.9214. At the equivalence point, indicate whether the pH of the resulting solution is acidic, basic or neutral for titrations of each of the following pairs of aqueous acids and bases. A) HClO4 with KOH _____________ B) Ca(OH)2 with HNO3 _____________ C) CH3COOH with LiOH _____________ D) HCN with NH3 _____________ E) HI with NH3 _____________ Answer: A) neutral B) neutral C) basic D) basic E) acidic 15. Match the titrations described below (A-E) to one of the titrations curves depicted below. A) NaOH added to HF B) HCl added to NH3 C) HNO3 added to KOH D) KOH added to HBr E) NH3 is added to HNO2 Answer: I-C, II-E, III-B, IV-A,