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802 Chapter 14 | Acid-Base Equilibria
96. What is the effect on the concentration of ammonia, hydroxide ion, and ammonium ion when the following are added to a basic buffer solution of equal concentrations of ammonia and ammonium nitrate:
(a) KI
(b) NH3
(c) HI
(d) NaOH
(e) NH4Cl
97. What will be the pH of a buffer solution prepared from 0.20 mol NH3, 0.40 mol NH4NO3, and just enough water to give 1.00 L of solution?
98. Calculate the pH of a buffer solution prepared from 0.155 mol of phosphoric acid, 0.250 mole of KH2PO4, and enough water to make 0.500 L of solution.
99. How much solid NaCH3CO2•3H2O must be added to 0.300 L of a 0.50-M acetic acid solution to give a buffer with a pH of 5.00? (Hint: Assume a negligible change in volume as the solid is added.)
100. What mass of NH4Cl must be added to 0.750 L of a 0.100-M solution of NH3 to give a buffer solution with a pH of 9.26? (Hint: Assume a negligible change in volume as the solid is added.)
101. A buffer solution is prepared from equal volumes of 0.200 M acetic acid and 0.600 M sodium acetate. Use 1.80 10−5 as Ka for acetic acid.
(a) What is the pH of the solution? (b) Is the solution acidic or basic?
(c) What is the pH of a solution that results when 3.00 mL of 0.034 M HCl is added to 0.200 L of the original buffer?
102. A 5.36–g sample of NH4Cl was added to 25.0 mL of 1.00 M NaOH and the resulting solution diluted to 0.100 L.
(a) What is the pH of this buffer solution?
(b) Is the solution acidic or basic?
(c) What is the pH of a solution that results when 3.00 mL of 0.034 M HCl is added to the solution?
103. Which acid in Table 14.2 is most appropriate for preparation of a buffer solution with a pH of 3.1? Explain
your choice.
104. Which acid in Table 14.2 is most appropriate for preparation of a buffer solution with a pH of 3.7? Explain your choice.
105. Which base in Table 14.3 is most appropriate for preparation of a buffer solution with a pH of 10.65? Explain your choice.
106. Which base in Table 14.3 is most appropriate for preparation of a buffer solution with a pH of 9.20? Explain your choice.
107. Saccharin, C7H4NSO3H, is a weak acid (Ka = 2.1 10−2). If 0.250 L of diet cola with a buffered pH of 5.48 was prepared from 2.00 10−3 g of sodium saccharide, Na(C7H4NSO3), what are the final concentrations of saccharine and sodium saccharide in the solution?
108. What is the pH of 1.000 L of a solution of 100.0 g of glutamic acid (C5H9NO4, a diprotic acid; K1 = 8.5 10−5, K2 = 3.39 10−10) to which has been added 20.0 g of NaOH during the preparation of monosodium glutamate, the flavoring agent? What is the pH when exactly 1 mol of NaOH per mole of acid has been added?
14.7 Acid-Base Titrations
109. Explain how to choose the appropriate acid-base indicator for the titration of a weak base with a strong acid.
110. Explain why an acid-base indicator changes color over a range of pH values rather than at a specific pH.
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