Name ______________________________________________ Date ____________________ Period ____
Homework
Chapter 17: Additional Aspects of Aqueous Equilibria
Exercises: Sections 17.2: Buffers
1. For a buffered solution, what factors determine
(a) the pH
(b) the buffer capacity
2. Write the Henderson-Hasselbach equation and explain its significance:
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3.
(a) Calculate the pH of a buffer that is 0.100 M in NaHCO3 and 0.125 M in Na2CO3. Try it the “Old
Way” using the method taught in Chapter 16, (Ka2 for carbonic acid and the equilibrium expression
for the dissociation of HCO3 – ) and the “New Way” using the Henderson-Hasselbach equation.
(b) Calculate the pH of a solution formed by mixing 55 mL of 0.20 M NaHCO3 with 65 mL of 0.15 M
Na2CO3. (Just use the “New Way” employing the Henderson-Hasselbach equation.
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4. A buffer is prepared by adding 5.0 g of ammonia, NH3, and 20.0 g of ammonium chloride, NH4Cl, to
enough water to form 2.50 L of solution.
(a) What is the pH of this buffer?
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4. Continued:
(b) Write the complete and net ionic equation for the reaction that occurs when a few drops of nitric
acid are added to the buffer/
(c) Write the complete and net ionic equation for the reaction that occurs when a few drops of
potassium hydroxide solution are added to the buffer.
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5. How many grams of sodium lactate, NaC3H5O3, should be added to 1.00 L of 0.150 M lactic acid, HC3H5O3,
to form a buffer solution with pH 3.90? Assume that no volume change occurs when the NaC3H5O3 is
added.
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6. A buffer, consisting of H2PO4 – and HPO42 – , helps control the pH of physiological fluids. Many carbonated soft drinks also use
this buffer system. What is the pH of a soft drink in which the major buffer ingredients are 6.5 g of NaH 2PO4 and 8.0 g of
Na2HPO4 per 355 mL of solution?
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7. A buffer solution contains 0.12 mol of propionic acid, HC3H5O2, and 0.10 mol of sodium propionate,
NaC3H5O2, in 1.50 L.
(a) What is the pH of this buffer?
(b) What is the pH of the buffer after the addition of 0.01 mol of NaOH?
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7. (b) Continued:
(c) What is the pH of the buffer after the addition of 0.01 mol of HI?
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7. (c) Continued:
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