Chemistry (Chang), 10th Edition

Chapter 16: Acid-Base Equilibria and Solubility Equilibria

Self Assessment A

1
What is the pH of a sodium formate/formic acid buffer solution containing equal concentrations of both buffer components? [Ka formic acid = 1.7 x 10-4]
A)7.0
B)6.2
C)3.8
D)3.0
E)We cannot determine the pH of the buffer solution unless we know the actual concentrations of the buffer components
2
A buffer solution is prepared by dissolving 0.10 mol of acetic acid and 0.10 mol of sodium acetate in 1 L of solution. A 10-mL portion of 1 M HCl is then added to the solution. How much does the addition change the pH of the buffer? [Ka(CH3COOH) = 1.8 x 10-5]
A)0.88 pH units
B)0.12 pH units
C)1.2 pH units
D)0.087 pH units
E)0.82 pH units
3
Which of the following combinations, when dissolved in equimolar amounts in water, would produce a buffer solution?
A)NaCl and NaC2H3O2
B)HC2H3O2 and NaCl
C)HNO3 and NaOH
D)NaNO3 and NH3
E)NH3 and NH4Cl
4
When an acid, HA, is titrated with 0.1 M NaOH, the pH at the half equivalence point of the titration is 4.5. What is the Ka of the acid?
A)3.2 x 10-5
B)3.2 x 10-10
C)1.8 x 10-3
D)7.0 x 10-7
E)HA is a strong acid
5
Methyl red is a commonly used acid-base indicator with a Ka of 6.3 x 10-6. The unionized form of methyl red (HIn) is red, and the ionized form (In-) is yellow. What color would a 1.0 x 10-2 M aqueous solution of methyl red have at pH = 4?
A)colorless
B)yellow
C)red
D)There's really no way to tell without preparing the solution and checking its color.
6
The solubility of AlF3 is 6.7 g AlF3 per liter of solution. The density of a saturated AlF3 solution is 1.0 g/mL. The Ksp of AlF3 is:
A)1.9 x 10-2
B)6.0 x 10-3
C)1.1 x 10-3
D)4.0 x 10-4
7
Calculate the concentration of calcium ions present in a saturated calcium phosphate solution. [Ksp Ca3(PO4)2 = 1.3 x 10-26]
A)1.2 x 10-5 M
B)2.0 x 10-5 M
C)2.6 x 10-6 M
D)7.8 x 10-6 M
E)8.3 x 10-6 M
8
The Ksp of PbI2 is 1.4 x 10-8. Calculate the molar solubility of PbI2 in 0.01 M NaI.
A)1.5 x 10-3 M
B)1.4 x 10-4 M
C)1.4 x 10-6 M
D)5.6 x 10-2 M
E)None of the above
9
Which of the following compounds is appreciably more soluble in 1 M HNO3 than in pure water?
A)FeCO3
B)AgBr
C)BaSO4
D)NaNO3
E)NaCl
10
Silver chloride is insoluble in water, but soluble in NH3 solution because NH3
A)raises the solution pH, and AgCl dissolves in basic solutions.
B)lowers the solution pH, and AgCl is soluble in acidic solutions.
C)complexes Cl-, shifting the equilibrium and allowing AgCl to dissolve.
D)complexes Ag+, shifting the equilibrium and allowing AgCl to dissolve.
11
A buffer system helps maintain the pH of blood plasma.
A)True
B)False
12
What is the pH of a buffer solution prepared by mixing 50.0 mL of 0.022 M C6H3COOH(aq) and 20.0 mL of 0.032 M NaC6H5CO2(aq)?
A)3.95
B)1.26
C)7.42
D)8.63
13
Which of the following is incorrect concerning a buffer?
A)A buffer is a combination of a weak acid with its salt.
B)A buffer is a combination of a weak base with its salt.
C)A buffer can resist all changes in pH.
D)Buffers are important to living organisms.
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