Dr. Herrick's CH223
Pressure Quiz 4

     

 

                               

Acid-Base Titrations and Buffers
Copyright  D. Herrick

 

20 Questions from past exams.
Practice for speed.  Aim for 2 minutes per problem.
(all concentrations in molarity units)

 

                                

1. After neutralization, the pH of a solution prepared as 0.013 M HCl and 0.010 M NaOH is
A) 4.81 B) 2.52 C) 4.13 D) 7.00 E) 2.08

                                

2. The pH of a solution prepared as 0.010 M HCl and 0.015 M NaOH is:
A) 9.98 B) 2.30 C) 11.7 D) 9.87 E) 12.8

    

3. Iodic acid HIO3 has Ka = 1.6 10 -1. Find the equilibrium constant of the neutralization reaction
HIO3 + OH -   IO3- + H2O
A) 1.6 1013 D) 4.7 1012
B) 5.8 104 E) 3.2 1013
C) 6.2 10-14 F) 2.4

                                

4. What volume of 0.0560 M NaOH is required to reach the equivalence point in the titration of 38.3 mL of 0.1250 M HIO3?
A) 38.3 mL B) 82.1 C) 88.4 D) 85.5 E) 76.6

                               

5. What volume of 0.1 M KOH is required to reach the buffer point in the titration of 50 mL of 0.3 M HIO3?
A) 25 mL B) 150  C) 50 D) 100  E) 75

   

animation of titration curve for a weak monoprotic acid

 

6. When 80 mL of 0.500 M formic acid (HCOOH, a weak acid) is titrated with 0.100 M NaOH the order of concentrations at the starting point is: 
A) [ HCOOH ] > [ HCOO- ]
B) [ HCOOH ] = [ HCOO- ]
C) [ HCOO- ] > [ HCOOH ]

                                

7. When 40 mL of 0.200 M formic acid (HCOOH, a weak acid) is titrated with 0.200 M NaOH the order of concentrations at the equivalence point is:
A) [ HCOO- ] > [ HCOOH ]
B) [ HCOOH ] = [ HCOO- ]
C) [ HCOOH ] > [ HCOO-

                                

8. When 56 mL of 0.250 M formic acid (HCOOH, a weak acid) is titrated with 0.125 M NaOH the order of concentrations at the buffer point is: 
A) [ HCOO- ] > [ HCOOH ] 
B) [ HCOOH ] > [ HCOO-
C) [ HCOOH ] = [ HCOO-

          

9. The pH of a solution prepared as 0.80 M benzoic acid (C6H5COOH,  Ka = 6.3 10-5) and 1.15 M  C6H5COONa  is:
A) 4.29 B) 4.36 C) 4.04  D) 4.20   E) 4.11 

                                 

10. When the pH of a solution containing acetic acid CH3COOH (Ka = 1.80 10-5) is adjusted to 7.40 the ratio [CH3COO-] / [CH3COOH] is:
A) 452 B) 314 C) 549 D) 185  E) 1/296 
        

animation of distribution diagram for a weak monoprotic acid

 

 

11. The pH of a solution prepared as 1.10 M C6H5COOH (benzoic acid, Ka = 6.3 10-5) and 0.90 M  C6H5COOK  is:
A) 4.29 B) 4.53   C) 3.87 D) 4.11   E) 4.20 

                             

12. A solution having equal concentrations of acetic acid CH3COOH (Ka = 1.8 10-5) and  CH3COONa has pH = 
A) 4.74 B) 4.53   C) 5.07 D) 4.11   E) 4.20 

    

13. A solution having equal equilibrium concentrations of NH3 (Kb = 1.8 10-5) and NH4Cl has [OH-] =
A) 4.24 10-3 D) 5.56 10-10
B) 1.34 10-3 E) 3.60 10-5
C) 2.53 10-4 F) 1.80 10-5

    

14. What's [H+] in a solution prepared by mixing 0.10 mol of hydrochloric acid HCl and 0.10 mol of ammonia NH3 (Kb = 1.80 10-5) in 1.00 L of water?
A)  9.11 10-4 D) 2.85 10-6
B)  3.73 10-9 E) 1.80 10-5
C)  7.45 10-6 F) 1.39 10-6

                                 

15. Potassium hydroxide KOH is added to a solution of hypochlorous acid HOCl (Ka = 2.9 10-8).  At pH = 7.00 the ratio [KOCl] / [HOCl] is:
A) 58 B) 0.29 C) 14.5  D) 1.00   E) 0.43  

                                 

16. How many mols of sodium nitrite NaNO2 should be added to 0.50 L of 0.20 M nitrous acid  (HNO2,  Ka = 7.10 10-4)  to obtain a solution buffered at pH = 3.40?
A) 0.178 B) 0.246 C) 0.285  D) 0.193   E) zero  

                               

17. What's the pH after 20 mL of 1.00 M NaOH and 500 mL of 0.10 M  CH3COOH  (acetic acid,  pKa = 4.74) are mixed?
A) 4.74 B) 5.06 C) 4.38  D) 2.99   E) 4.56  

     

18. What's  the pH after 50 mL of 0.10 M NaOH and 50 mL of 0.10 M HCOOH  (formic acid, Ka = 1.80 10-4 ) are mixed?
A) 7.48 B) 9.26 C) 8.22  D) 7.00   E) 8.72 

                               

19. A solution prepared as 0.5 M CH3CH2COOH (propanoic acid) and 0.5 M CH3CH2COONa has pH = 4.886.  Ka for propanoic acid is:
A) 1.30 10-5 D) 1.72 10-5
B) 2.41 10-4 E) 1.69 10-10
C) 1.53 10-5 F) 8.66 10-5

                                  

20. You are asked to adjust the pH of a solution that contains 0.5M acetic acid CH3COOH (Ka = 1.80 10-5) by titrating it with NaOH to a point where the solution has [CH3COO-] = 10   [CH3COOH].  At what pH should you stop adding NaOH?
A) 8.43 B) 3.74 C) 8.92  D) 5.74   E) 9.26 

 

 

 


 

 

   Copyright  D. Herrick