1. Calculate the Ph of Each of the Following Solutions

CH 15 HOMEWORK

1. Calculate the pH of each of the following solutions:

(a) 0.100 M HONH2 (Kb = 1.1 x 10-8)

(b) 0.100 M HONH3Cl

(c) Pure water

(d) A mixture containing 0.100 M HONH2 and 0.100 M HONH3Cl

2. Calculate the percent dissociation of the solutions in 1(a) and 1(d). Explain any difference.

3. Calculate the pH after 0.10 mol of NaOH is added to a 1.00L buffer solution consisting of 0.60 M HF (Ka = 7.2 x 10-4) and 1.00 M KF.

4. Calculate the pH after 0.20 mol of HCl is added to a 1.00 L buffer solution consisting of 1.00 M HNO2(Ka = 4.0 x 10-4) and 1.00 M NaNO2.

5. A buffered solution is made by adding 50.0g of NH4Cl to 1.00 L of a 0.75 M solution of NH3

(Kb = 1.8 x 10-5). Calculate the pH of the final solution.

6. Calculate the pH after 0.10 M NaOH is added to a buffer solution consisting of 0.50 M CH3NH2

(Kb = 4.38 x 10-4) and 0.70 M CH3NH3Cl.

7. Calculate the pH after 0.15 mol solid NaOH is added to 1.00 L of each of the buffered solutions:

(a) 0.050 M propanoic acid (HC3H5O2, Ka = 1.3 x 10-5) and 0.080 m sodium propanoate.

(b) 0.50 M propanoic acid and 0.80 M sodium propanoate.

(c) Is the solution in part (a) still a buffered solution after the NaOH has been added? Explain.

8. Using the bases in Table 14.3, which base would be the best choice for preparing a pH = 5.00 buffer? Explain how to make 1.0L of this buffer.

9. Sketch the titration curve for the titration of a generic weak acid HA with a strong base. The titration reaction is:

HA + OH- ↔ A- + H2O

On the curve indicate the points that correspond to the following:

(a) the stoichiometric (equivalence) point

(b) the region with maximum buffering

(c) pH = pKa

(d) pH depends only on [HA]

(e) pH depends only on {A-]

(f) pH depends only on the amount of excess strong base added

10. Calculate the pH of a solution that is 0.50 M CH3NH2 and 0.70 M CH3NH3Cl.

11. Calculate the pH after 0.10 mol of NaOH is added to 1.00 L of the solution in Problem #10.

12. Consider the titration of 100.0 mL of 0.200 M acetic acid (Ka = 1.8 x 10-5) by 0.100 M KOH. Calculate the pH of the resulting solution after the following volumes of KOH have been added:

(a). 0.0 mL KOH

(b). 50.0 mL KOH

(c). 100.0 mL KOH

(d). 150 mL KOH

13. A sample of a certain monoprotic weak acid was dissolved in water and titrated with 0.125 M NaOH, requiring 16.00 mL to reach the equivalence point. During the titration, the pH after adding 2.00 mL of NaOH was 6.912. Calculate the Ka for the weak acid.

14. Two drops of indicator HIn (Ka = 1.0 x 10-9), where HIn is yellow and In- is blue, are placed in

100.0 mL of 0.10 M HCl.

(a). What color is the solution initially?

(b). The solution is titrated with 0.10 M NaOH. At what pH will the color change (yellow to greenish yellow) occur?

(c). What color will the solution be after 200.0 mL of NaOH has been added?

15. A solution has a pH of 4.5. What would be the color of the solution if each of the following indicators were added? (Use Fig. 15.8 on page 756)

(a). methyl orange

(b). alizarin

(c). bromcresol green

(d). phenolphthalein

16. Write balanced equations and the corresponding solubility product expressions for the dissolution of each of the following solids:

(a). Ag2CO3

(b). Ce(IO3)3

(c). BaF2

17. Use the following data to calculate the Ksp value for each solid.

(a). The solubility of Pb3(PO4)2 is 6.2 x 10-12 mol/L

(b). The solubility of Li2CO3 is 7.4 x 10-2 mol/L

18. The concentration of Ag+ in a solution saturated with Ag2C2O4 (s) is 2.2 x 10-4 M.

Calculate Ksp for Ag2C2O4 .

19. The Ksp for cadmium carbonate (CdCO3) is 5.2 x 10-12. Calculate its solubility in moles/L.

20. For each of the following pairs of solids, determine which solid has the smallest molar solubility.

(a). CaF2 (Ksp = 4.0 x 10-11) or BaF2 (Ksp = 2.4 x 10-5)

(b). Ca3(PO4)2 (Ksp = 1.3 x 10-32) or FePO4 (Ksp = 1.0 x 10-22). Hint: You must calculate the solubility of each in order to make the determination.

21. The Ksp for silver sulfate (Ag2SO4) is 1.2 x 10-5. Calculate the solubility of silver sulfate in each of the following.

(a). Pure water

b). 0.10 M AgNO3

(c). 0.20 M K2SO4

22. For which salt in each of the following groups will the solubility depend on pH?

(a). AgF, AgCl, AgBr

(b). Pb(OH)2, PbCl2

(c). Sr(NO3)2, Sr(NO2)2

(d). Ni(NO3)2, Ni(CN)2

23. Calculate the final concentrations of K+ (aq), C2O42- (aq), Ba2+ (aq), and Br- (aq) in a solution prepared by adding 0.100 L of 0.200 M K2C2O4 to 0.150 L of 0.250 M BaBr2 . (For BaC2O4, the Ksp = 2.3 x 10-8).

24. A solution contains 1.0 x 10-5 M Na3PO4. What is the minimum concentration of AgNO3 that would cause precipitation of solid Ag3PO4 (Ksp = 1.8 x 10-18)?

25. Write the equations for the stepwise formation of each of the following complex ions.

(a). Co(NH3)63+

(b). Ni(CN)42-

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