Practice Problems and Review Chem 121—Fall 2005
Note: For some of the problems you will need to use the table of Ka values from your text.
1. Write the chemical equation that represents HCO3- acting as a base in water.
HCO3- + H2O H2CO3 + OH-
Write the chemical equation that represents HCO3- acting as an acid in a reaction with HSO3-.
HCO3- + HSO3- CO32- + H2SO3
2. Write the chemical formula for the conjugate acid of NH3. NH4+
3. What is the pH of a 1.0 x 10-3 M solution of HNO3? 3.0
What is the pH of 25.0 mL of 1.0 x 10-3 M solution of HNO3? 3.0
4. What is the pH of a 1.0 x 10-3 M solution of HCN? x2 = 4.0 x 10-10 · (1.0 x 10-3); pH = 6.20
5. What is the pH of a 2.0 x 10-3 M solution of Ba(OH)2? pH = 11.60
6. What is the pH of a 0.200 M solution of Na2CO3? pH = 11.78
7. What is the pH of a solution containing 0.030 M HNO2 and 0.020 M NaNO2? pH = 3.17
8. What is the pH of a solution prepared by mixing 25.0 ml of 0.100 M HCl with 45.0 ml of
0.075 M KOH? pH = 12.10
9. What is the pH of a solution prepared by mixing 25.0 ml of 0.100 M HCl with 45.0 ml of
0.075 M NaNO2? pH = 2.89
10. What would be the new pH of the solution in problem 9. if 0.0010 moles of NaOH is added to
it with no change in solution volume? pH = 3.44
11. In each pair, which solution will have the lower pH.
a. 0.10 M H2CO3 or 0.10 M HClO4
b. 0.10 M NH4Cl or 0.10 M KNO3
c. 0.10 M NaOH or 0.10 M Na2CO3
d. 0.10 M NaF or 0.10 M NaCl
e. 0.10 M HF or 0.10 M HNO2
12. Is a solution of NaHSO3 acidic or basic? Ka = 5.6 x 10-8 and Kb = 5.9 x 10-13 acidic
13. Is a solution of NH4F acidic or basic? acidic because Ka > Kb
a solution of NH4C2H3O2? neutral
14. What is the [H3O+] in a solution with a pH of 6.03? 9.3 x 10-7
What is the [OH-] in a solution with a pH of 6.03? 1.1 x 10-8
15. Arrange the following in order of increasing acid strength. HB < HC < HA
HA, pK a= 2.3, HB, pKa = 9.2 HC, pKa = 6.6
16. Write the names and formulas of the six strong acids. See table 12-1
17. Write the names and formulas of five strong bases. See table 12-1
18. The Ka1 for H2CrO4 is 1 x 10-2 and the Ka2 is 3.2 x 10-7. What is the pKa for H2CrO4? What are
the Kb and pKb for HCrO4-. pKa = 2.0; Kb = 1.0 x 10-12 pKb = 12.0
19. What weak acid/base pair would you use to make a buffer with a pH of 4.5. HOAc/NaOAc
If the concentration of the weak acid is 0.100 M in 1.00 liter of solution, how many moles of
the weak base would you add to get a pH of 4.5? 0.056 mol NaOAc
