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To get the class handouts for Acid-Base Equilibrium, click HERE.

Here are some typical exam questions

about acid-base equilibrium and salts.

The following constants may be useful:
HC2H3O2 Ka = 1.8 x 10-5 NH3(aq) Kb = 1.8 x 10-5
HCN Ka = 6.2 x 10-10 CH3NH2(aq) Kb = 4.4 x 10-4
HC3H5O2 Ka = 1.3 x 10-5 C5H5N(aq) Kb = 1.5 x 10-9
HF Ka = 6.8 x 10-4 N2H4(aq) Kb = 9.6 x 10-7
C6H5NH2(aq) Kb = 4.1 x 10-10
H3PO4 Ka1 = 7.1 x 10-3 ;  Ka2 = 6.3 x 10-8 ; Ka3 = 4.5 x 10-13
1. Consider a solution that has a hydronium ion concentration of 4.3 x 10-8 M. What is the hydroxide ion molarity in this solution?
a. [OH-] = 2.3 x 10-7 d. [OH-] = 4.3 x 10-6
b. [OH-] = 1.0 x 10-14 e. [OH-(aq)] = [H+(aq)]
c. [OH-] < [H+(aq)]

 

2. Which of the following is true concerning a 0.10 M solution of HF?
a. pH > 7.0 d. [OH-] > [H+(aq)]
b. [H+(aq)] = [OH-] e. [F-] = 0.10 M
c. pH < 7.0
3. The conjugate acid of HCO3- is:
a. H2O d. H2CO3
b. OH- e. H3O+
c. CO32-

 

4. The pOH of a 0.10 M solution of a weak base is 4.92. The Kb for this weak base is:
a. 1.6 x 10-6 d. 8.3 x 10-10
b. 8.3 x 10-9 e. 1.2 x 10-5
c. 1.4 x 10-9

 

5. What is the pH of a 0.10 M solution of a weak acid, HA, that has a Ka = 4.17 x 10-6?
a. 2.82 d. 7.00
b. 3.19 e. 2.48
c. 4.66

 

6. Which of the following aqueous solutions has the highest pH? All are 0.10 M.
a. NH4I d. NaNO2
b. NaI e. HI
c. HNO2

 

7. The ion-product constant, Kw, for water increases as temperature increases. At body temperature, 37oC, Kw = 5.00 x 10-14. What is neutral pH at body temperature?
a. 7.00 d. 6.00
b. 6.65 e. 7.35
c. 7.50

Assume you have to calculate the pH of each of the following mixtures (questions 8 through 13). For each one, indicate how the solution would be treated in the calculation:

8. 0.500 mole of HCl and 0.800 mole of HC2H3O2 in 1.0 L of solution.
a. a strong acid solution d. a weak base solution
b. a weak acid solution e. a buffer solution
c. a strong base solution f. a neutral solution

 

9. 0.500 mole of NH3(aq) and 0.250 mole of HNO3in 1.0 L of solution.
a. a strong acid solution d. a weak base solution
b. a weak acid solution e. a buffer solution
c. a strong base solution f. a neutral solution

 

10. 0.300 mole of NaH2PO4 and 0.300 mole of NaCl in 1.0 L of solution.
a. a strong acid solution d. a weak base solution
b. a weak acid solution e. a buffer solution
c. a strong base solution f. a neutral solution

 

 

11. 0.250 mole of KOH and 0.400 mole of HC2H3O2 in 1.0 L of solution.
a. a strong acid solution d. a weak base solution
b. a weak acid solution e. a buffer solution
c. a strong base solution f. a neutral solution

 

12. 0.085 mole of NaH2PO4 and 0.065 mole of H3PO4 in 1.0 L of solution.
a. a strong acid solution d. a weak base solution
b. a weak acid solution e. a buffer solution
c. a strong base solution f. a neutral solution

 

 

13. 0.250 mole of N2H5Cl in 1.0 L of solution.
a. a strong acid solution d. a weak base solution
b. a weak acid solution e. a buffer solution
c. a strong base solution f. a neutral solution

 

14. For equal volumes of 0.1500 M solutions of hydrochloric acid, HCl (Ka = very large), formic acid, HCHO2 (Ka = 1.7 x 10-4), acetic acid, HC2H3O2 (Ka = 1.7 x 10-5) and nitrous acid, HNO2 (Ka = 4.5 x 10-4), which requires the largest volume of 0.1000 M NaOH to titrate to the equivalence point?
a. HCl d. HNO2
b. HCHO2 e. all require the same volume
c. HC2H3O2

 

 

15. What is the pH of a solution that is 2.66 x 10-2 M in Ca(OH)2?
a. 1.58 d. 1.27
b. 10.85 e. 12.42
c. 12.73

 

16. Lewis defined an acid as:
a. a proton donor d. anything that can accept an electron pair
b. an electron pair donor e. a proton acceptor
c. any species that can increase the proton concentration in water

 

17. Ultimately, which of the following is the strongest acid in water?
a. hydronium ion d. HClO
b. HC2H3O2 e. HCl
c. HClO4

 

18. Which of the following species would not act as an acid in water?
a. H2CO3 d. HSO3-
b. HCO3- e. H3PO4
c. HSO4-

 

19. Which solution is most acidic?

a. [OH-] = 2.4 x 10-4

d. [H+(aq)] = 5.5 x 10-9
b. [OH-] = 8.2 x 10-10 e. [H+(aq)] = 1.1 x 10-5
c. [H+(aq)] = 9.3 x 10-8

 

20. What is the pH of 750 mL of 0.650 M nitric acid? (The FW of nitric acid is 63.0.)
a. 0.19 d. 0.31
b. 0.062 e. insufficient data given to calculate the pH
c. 0.65

 

21. Each of the following net-ionic equations describes an acid-base reaction. Write the formula for the requested species in the blank.
(a) [Al(H2O)6]3+(aq) + H2O(l) ----->   [Al(H2O)5OH]2+(aq) + H3O+(aq)
The Bronsted-Lowry acid:    [Al(H2O)6]3+(aq)
The Bronsted-Lowry conjugate acid: H3O+(aq)
(b) C5H5N:   +  H2O(l)  ----->  C5H5N:H+ (aq)  +  OH-(aq)
The Lewis acid is: H+
The Lewis base is:  C5H5N:

 

22. Several solutions are listed below; Indicate with an "X" in the appropriate column whether they would be acidic, basic, or neutral.

 
Solution acidic neutral basic
0.10 M KCN     X
0.25 M AlCl3 X    
0.30 M NH4Br X    
0.10 M NaNO3   X  
0.25 M CH3NH3I X    
0.20 M NaH2PO4 X    

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