Workshop CHE 168
Problem Set #6
1. Calculate the concentration of H3O+ (aq) in
(a) a solution in which [OH-] is 0.010 M
(b) a solution in which [OH-] is 2.0 x 10-9 M
(c) [OH-] = 2 x 10-5 M
2. Indicate whether each of the following solutions is neutral, acidic or basic:(a) [H3O+] = 2 x 10-5 M
(b) [OH-] = 3 x 10-9 M
(c) [OH-] = 1 x 10-7 M
3. Write the conjugate base of each of the following: HClO4 (aq), H2S (aq), PH4+ (aq), HCO3- .4. Write the conjugate acid of each of the following: CN- , SO42- , H2O, HCO3- .
5. When lithium oxide, Li2O, is dissolved in water, the solution turns basic from the reaction of the oxide ion, O2-, with water. Write the reaction that occurs and identify the conjugate acid-base pairs.
6. Write the reaction that occurs when formic acid, HCHO2 (aq), dissociates and identify the conjugate acid-base pairs.
7. Hydrocyanic acid, HCN, is ionized in water to a lesser extent than an HF solution of the same concentration. What is the conjugate base of HCN? Is it a stronger or weaker base than F-?
8. In a sample of lemon juice, [H3O+] = 3.8 x 10-4 M. What is the pH and the pOH?
9. An aqueous solution has a pH of 8.76. What is the pOH? Calculate the H3O+ concentration?
10. What is the pH of a0.040 M solution of HClO4?
11. An aqueous solution of HNO3 (aq) has a pH of 2.66. What is the concentration of the acid?
12. What is the pH of a 0.011 M solution of Ca(OH)2 (aq)?
13. A student prepared a 0.10 M solution of formic acid, HCHO2 (aq), and found the pH to be 2.38.
(a) Calculate the Ka for formic acid
(b) determine the per cent ionization of the formic acid in this solution
14. Calculate the pH of a 0.20 M solution of HCN (aq). Is the approximation method valid? [Ka = 4.9 x 10-10].