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Chapter 14 Part II Self Quiz


Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
 

 1. 
Given a solution of 0.10 M NH3(aq), what is the effect of adding NH4Cl(s) to this solution?

1.
The pH will decrease.
2.
The concentration of NH3 will increase.
3.
The concentration of H3O+ will increase.
a.
1 only
b.
2 only
c.
3 only
d.
1 and 3
e.
1, 2, and 3
 

 2. 
What is the pH of an aqueous solution of 0.30 M HF and 0.15 M F-? (Ka of HF = 7.2 × 10-4)
a.
1.83
b.
2.84
c.
3.14
d.
3.44
e.
10.86
 

 3. 
Which of the following combinations would be best to buffer an aqueous solution at a pH of 2.0?
a.
H3PO4 and H2PO4-, Ka1 = 7.5 × 10-3
b.
HNO2 and NO2-, Ka = 4.5 × 10-4
c.
CH3CO2H and CH3COO-, Ka = 1.8 × 10-5
d.
H2PO4- and HPO42-, Ka2 = 6.2 × 10-8
e.
NH4+ and NH3, Ka = 5.7 × 10-10
 

 4. 
What is the pH of the buffer that results when 4.0 g of NH3 and 8.0 g of NH4Cl are diluted with water to a volume of 0.50 L? (Ka of NH4+ = 5.6 × 10-10)
a.
8.95
b.
9.06
c.
9.25
d.
9.45
e.
9.55
 

 5. 
What is the pH of a buffer that results when 33 g NaHCO3 is mixed with 100.0 mL of 2.50 M NaOH and diluted with water to 250 mL? (Ka for HCO3- = 4.8 × 10-11)
a.
8.20
b.
10.07
c.
10.12
d.
10.32
e.
10.56
 

 6. 
A buffer is prepared by combining 250 mL of 0.25 M NaOH and 250 mL of a 0.600 M weak acid, HA. If the pH of the buffer is 6.33, what is the pKa of the acid?
a.
5.95
b.
6.18
c.
6.33
d.
6.48
e.
6.71
 

 7. 
How many moles of HCl must be added to 1.00 L of 0.72 M NH3 to make a buffer with a pH of 9.50? (Ka of NH4+ = 5.6 × 10-10)
a.
0.26 mol
b.
0.31 mol
c.
0.41 mol
d.
0.46 mol
e.
1.3 mol
 

 8. 
A volume of 25.0 mL of 0.100 M HCO2H(aq) is titrated with 0.100 M NaOH(aq). What is the pH after the addition of 12.5 mL of NaOH? (Ka for HCO2H = 1.8 × 10-4)
a.
2.52
b.
3.74
c.
4.74
d.
7.00
e.
10.26
 

 9. 
A 25.0 mL sample of 0.0200 M NH3(aq) is titrated with 0.0100 M HCl(aq). What is the pH at the equivalence point? (Kb of NH3 = 1.8 × 10-5)
a.
3.46
b.
5.48
c.
5.72
d.
8.25
e.
10.54
 

 10. 
Potassium hydrogen phthalate (molar mass = 204.2 g/mol) is used to standardize sodium hydroxide. If 26.37 mL of NaOH(aq) is required to titrate 0.7719 g KHP to the equivalence point, what is the concentration of the NaOH(aq)?

HC8H4O4-(aq) + OH-(aq) double sided arrow C8H4O42-(aq) + H2O(l)
a.
0.02036 M
b.
0.02937 M
c.
0.09968 M
d.
0.1433 M
e.
5.977 M
 



 
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