# Graph #1 on the following page shows the titration

More Exam #2 Practice Problems1. Graph #1 on the following page shows the titration curve for the titration of 20.0 mL of H2A with 0.240 M NaOH.a) After 20.0 mL of the base solution have been added, the pH is 4.00. Use this information to calculate K a1 for H2A.b) After 40.0 mL of the base solution have been added, the pH is 8.00. Use this information to calculate Ka2 for H2A.Then, Calculate the pH at:c) 0 mL of NaOH addedd) 10.0 mL of NaOH addede) 30.0 mL of NaOH addedf) 50.0 mL of NaOH addedg) 60.0 mL of NaOH addedh) 70.0 mL of NaOH added2. Graph #2 on the following page shows the titration curve for the titration of 20.0 mL of a weak base(B) with 0.100 MHCl.After 10.0 mL of HCl have been added, the pH is 5.77. Use this information to calculate Kb for the weak base.Then, calculate the pH at:a) 0 mL of HCl addedb) 20.0 mL of HCl addedc) 25.0 mL of HCl addedd) 30.0 mL of HCl added2+2+3. A solution is known to be 0.10 M in both Pb and Sn .–28a) What molarity of sulfide ion will produce the greatest amount of lead sulfide (Ksp = 8.0 x 10 ) precipitate without–25precipitating any tin(II) sulfide(Ksp = 1.0 x 10 )?2+b) What [Pb ] will remain dissolve (not precipitated) in this solution after you adjust the sulfide concentration to the value2+calculated in part a? What percentage of the original Pb in the solution has precipitated?4. A solution is made by dissolving 1.50 g of Cd(NO3)2 in 500. mL of 0.50 M NaCN. Kf for [Cd(CN)4]What are the molarities of the following species in the resulting 500 mL of solution?2–2+–a) [Cd(CN)4]b) Cdc) CN2–= 7.1 x 10165. How many mmoles of ammonia would have to be added to 300. mL of 0.10 M cupric sulfate in order to reduce the Cu–82+12concentration to 1.0 x 10 ? Kf for [Cu(NH3)4] = 5.0 x 10Assume no change in volume.2+6. The pH of a 0.25 M solution of pyridine (C5H5N) in water is 9.29.a) From this information, calculate the value of Kb for pyridine.b) What would be the pH of the solution made by adding 0.10 mole of HCl to 1.0 L of this pyridine solution?7. How many grams of sodium benzoate (MM 144) should be added to 200. mL of 1.0 M benzoic acid (HC7H5O2, Ka = 6.5–5x 10 ) to prepare a buffer with a pH of 4.00?8. If 15.0 mL of 0.50 M NaOH is added to 100. mL of the buffer solution prepared in problem #7 above, what would be thepH of the resulting solution?Answers:1. a) 2.0 x 10-4b) 5.0 x 10-9c) 2.07 d) 3.40 e) 6.00 f) 8.60 g) 10.63 h) 12.432. a) 9.34 b) 4.99 c) 3.42 d) 2.004. a) 0.0127 b) 4.4 x 107. 19g8. 4.1-18c) 0.453. a) 1.0 x 10-245. 131 mmoles-4b) 8.1 x 10 , > 99% of the lead ion has precipitated6. a) 1.5 x 10-9b) 5.35

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