Dr. Herrick's CH223
Pressure Quiz 5

     

 
   

More Titrations, Ionic Equilibria
Copyright  D. Herrick
 

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

 
  
Several questions involve sulfurous acid, H2SO3, which has 
     Ka1  =  1.4 Χ 10 -2  ,       Ka2  =  6.5 Χ 10 -8.
  
1. Use appropriate combinations of the Bronsted reactions for Ka, Kb, and Kw to determine which equilibrium constant is NOT correct for the neutralization reaction (1 minute each):
A) H2SO3 + OH- HSO3- + H2O ,  K = 1.4 Χ 1012
B) HSO3- + OH- SO32- + H2O ,  K = 6.5 Χ 106
C) SO32- + 2H3O+ H2SO3 + 2H2O,  K = 1.1 Χ 109
D) HSO3- + H3O+ H2SO3 + H2O,  K = 7.1 Χ 101
E) SO32- + H2SO3 2HSO3- ,  K = 2.2 Χ 105
F) OH- + H3O+  2H2O,  K = 1.0 Χ 1014

G) 

none of the above
    
  
2. What volume of 0.10 M NaOH will titrate 50 mL of 0.1 M H2SO3 to the first equivalence point?
A) 25 mL B) 50 C) 75  D) 100  E) 125
  
3. What volume of 0.10 M NaOH will titrate 50 mL of 0.1 M H2SO3 to the second equivalence point?
A) 25mL B) 50 C) 75  D) 100 E) 125

    
4. What volume of 0.10 M NaOH will titrate 50 mL of 0.1 M H2SO3 to the second buffer point?
A) 25mL  B) 50 C) 75  D) 100  E) 125

             
 

animated titration curve for a weak diprotic acid
 

  

5.

[H+] in 0.1 M H2SO3 is:
(quadratic equation is needed here due to high degree of ionization)
A) 3.0 Χ 10-2 D) 3.5 Χ 10-2
B) 3.1 Χ 10-2 E) 3.7 Χ 10-2
C) 3.3 Χ 10-2 F) 3.9 Χ 10-2

  

6. [SO32-] in 0.1 M H2SO3 is:
A) 2.5 Χ 10-4 D) 9.1 Χ 10-9
B) 1.4 Χ 10-3 E) 3.9 Χ 10-12
C) 4.7 Χ 10-6 F) 6.5 Χ 10-8

         
7. A solution prepared as 0.10 M Na2SO3 has:
A) [ H2SO3 ]  >  [ HSO3 – ]  >  [ SO3 2 – ]
B) [ H2SO3 ]  =  [ HSO3 – ]  >  [ SO3 2 – ]
C) [ HSO3 – ]  >  [ H2SO3 ]  =  [ SO3 2 – ]
D) [ HSO3 – ]  =  [ SO3 2 – ]  >  [ H2SO3 ]
E) [ SO3 2 – ]  >  [ HSO3 – ]  >  [ H2SO3 ]
F) [ SO3 2 – ]  >  [ HSO3 – ]  =  [ H2SO3 ]

     

8. A solution prepared as 0.10 M NaHSO3 has:
A) [ H2SO3 ]  >  [ HSO3 – ]  >  [ SO3 2 – ]
B) [ H2SO3 ]  =  [ HSO3 – ]  >  [ SO3 2 – ]
C) [ HSO3 – ]  >  [ H2SO3 ]  =  [ SO3 2 – ]
D) [ HSO3 – ]  =  [ SO3 2 – ]  >  [ H2SO3 ]
E) [ SO3 2 – ]  >  [ HSO3 – ]  >  [ H2SO3 ]
F) [ SO3 2 – ]  >  [ HSO3 – ]  =  [ H2SO3 ]
  
9. A solution prepared as 0.10 M H2SO3 has:
A) [ H2SO3 ]  >  [ HSO3 – ]  >  [ SO3 2 – ]
B) [ H2SO3 ]  =  [ HSO3 – ]  >  [ SO3 2 – ]
C) [ HSO3 – ]  >  [ H2SO3 ]  =  [ SO3 2 – ]
D) [ HSO3 – ]  =  [ SO3 2 – ]  >  [ H2SO3 ]
E) [ SO3 2 – ]  >  [ HSO3 – ]  >  [ H2SO3 ]
F) [ SO3 2 – ]  >  [ HSO3 – ]  =  [ H2SO3 ]

  

10. A solution prepared as 0.10 M NaHSO3 and 0.10 M Na2SO3 has:
A) [ H2SO3 ]  >  [ HSO3 – ]  >  [ SO3 2 – ]
B) [ H2SO3 ]  =  [ HSO3 – ]  >  [ SO3 2 – ]
C) [ HSO3 – ]  >  [ H2SO3 ]  =  [ SO3 2 – ]
D) [ HSO3 – ]  =  [ SO3 2 – ]  >  [ H2SO3 ]
E) [ SO3 2 – ]  >  [ HSO3 – ]  >  [ H2SO3 ]
F) [ SO3 2 – ]  >  [ HSO3 – ]  =  [ H2SO3 ]

  

11. A solution prepared as 0.10 M NaHSO3 and 0.10 M H2SO3 has:
A) [ H2SO3 ]  >  [ HSO3 – ]  >  [ SO3 2 – ]
B) [ H2SO3 ]  =  [ HSO3 – ]  >  [ SO3 2 – ]
C) [ HSO3 – ]  >  [ H2SO3 ]  =  [ SO3 2 – ]
D) [ HSO3 – ]  =  [ SO3 2 – ]  >  [ H2SO3 ]
E) [ SO3 2 – ]  >  [ HSO3 – ]  >  [ H2SO3 ]
F) [ SO3 2 – ]  >  [ HSO3 – ]  =  [ H2SO3 ]
  
12. The pH after mixing 0.20 mol of H2SO3 and 0.30 mol of NaOH in 1.0 L of water is:
A) 7.2 B) 8.9  C) 2.1  D) 5.1 E) 9.5
  
13. At pH = 7.00 in a titration of H2SO3 the solution is expected to have
A) [ H2SO3 ]  >  [ HSO3 – ]  >  [ SO3 2 – ]
B) [ H2SO3 ]  >  [ SO3 2 – ]  >  [ HSO3 – ]
C) [ HSO3 – ]  >  [ H2SO3 ]  >  [ SO3 2 – ]
D) [ HSO3 – ]  >  [ SO3 2 – ]  >  [ H2SO3 ]
E) [ SO3 2 – ]  >  [ HSO3 – ]  >  [ H2SO3 ]
F) [ SO3 2 – ]  >  [ H2SO3 ]  >  [ HSO3 – ]

               

 

animated distribution diagram for a weak diprotic acid
 
                 
14. When the pH of a solution containing H2SO3 is adjusted to pH = 7.00 the ratio [SO32-] / [HSO3- ] is
A) 0.98 B) 0.88 C) 0.74  D) 0.65  E) 0.57

       

15. When 40 mL of 0.200 M H2SO3 is titrated with 0.125 M NaOH the pH at the first equivalence point is: 
A) 9.04 D) 7.19
B) 3.64 E) 6.33
C) 1.85 F) 4.52 

    
16. The pH after mixing 0.30 mol of H2SO3 and 0.15 mol of NaOH in 1.0 L of water is:
A) 5.7  B) 4.3 C) 8.6  D) 3.0  E) 1.9
  
17. The molar solubility of lead iodide (PbI2 , Ksp = 6.5 Χ 10 -9 ) in water is:
A) 1.9 Χ 10-3 D) 6.5 Χ 10-9
B) 1.2 Χ 10-3 E) 1.6 Χ 10-7
C) 8.3 Χ 10-4 F) 4.0 Χ 10-5

  

18. The molar solubility of lead iodide (PbI2 , Ksp = 6.5 Χ 10 -9 ) in a 0.15 M solution of potassium iodide KI is:
A) 1.9 Χ 10-6 D) 6.5 Χ 10-9
B) 1.2 Χ 10-4 E) 1.6 Χ 10-7
C) 8.1 Χ 10-5 F) 2.9 Χ 10-7
  
19. What’s the molar solubility of Ca(OH)2 (Ksp = 6.5 Χ10-6) in a 0.25M solution of KOH?
A) 2.6 Χ10-5 D) 5.3 Χ10-4
B) 2.2 Χ10-4 E) 1.0 Χ10-4
C) 6.5 Χ10-4  F) 4.1 Χ10-7
  
20. When NaOH is added slowly to a solution in which [Zn2+] = 1.0 Χ 10-6 the precipitate Zn(OH)2 will begin to form according to

Zn(OH)2 (s) Zn2+(aq) + 2 OH- (aq),  Ksp = 1.8 Χ 10-14

when the pH of the solution is:
A) 10.1 B) 8.6 C) 7.2  D) 9.0   E) 12.3 

 


 

 

   Copyright  D. Herrick