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- Tooth enamel is composed of hydroxyapatite, whose simplest formula is Ca5(PO4)3OH, and whose corresponding Ksp = 6.8 × 10^(-27). As discussed in the Chemistry and Life box on page 746, fluoride in fluorinated water or in toothpaste reacts with hydroxyapatite to form fluoroapatite, Ca5(PO4)3F, whose Ksp = 1.0 × 10^(-60). (b) Calculate the molar solubility of each of these compounds.
Problem 1
Problem 2a
The beaker on the right contains 0.1 M acetic acid solution with methyl orange as an indicator. The beaker on the left contains a mixture of 0.1 M acetic acid and 0.1 M sodium acetate with methyl orange. (a) Using Figures 16.8 and 16.9, which solution has a higher pH?
Problem 2b
The beaker on the right contains 0.1 M acetic acid solution with methyl orange as an indicator. The beaker on the left contains a mixture of 0.1 M acetic acid and 0.1 M sodium acetate with methyl orange. (b) Which solution is better able to maintain its pH when small amounts of NaOH are added? Explain. [Sections 17.1 and 17.2]
Problem 3
A buffer contains a weak acid, HA, and its conjugate base. The weak acid has a pKa of 4.5, and the buffer has a pH of 4.3. Without doing a calculation, state which of these possibilities are correct at pH 4.3. (a) 3HA4 = 3A-4, (b) 3HA4 7 3A-4, or (c) 3HA4 6 3A-4. [Section 17.2]
Problem 4a
The following diagram represents a buffer composed of equal concentrations of a weak acid, HA, and its conjugate base, A-. The heights of the columns are proportional to the concentrations of the components of the buffer. (a) Which of the three drawings, (1), (2), or (3), represents the buffer after the addition of a strong acid? [Section 17.2]
Problem 4c
The following diagram represents a buffer composed of equal concentrations of a weak acid, HA, and its conjugate base, A-. The heights of the columns are proportional to the concentrations of the components of the buffer. (c) Which of the three represents a situation that cannot arise from the addition of either an acid or a base? [Section 17.2]
Problem 5b
The following figure represents solutions at various stages of the titration of a weak acid, HA, with NaOH. (The Na+ ions and water molecules have been omitted for clarity.) To which of the following regions of the titration curve does each drawing correspond: (b) after addition of NaOH but before the equivalence point? [Section 17.3]
Problem 6a
Match the following descriptions of titration curves with the diagrams: (a) strong acid added to strong base. [Section 17.3]
Problem 6d
Match the following descriptions of titration curves with the diagrams: (d) strong base added to polyprotic acid. [Section 17.3]
- (a) Will Co(OH)2 precipitate from solution if the pH of a 0.020 M solution of Co(NO3)2 is adjusted to 8.5? (b) Will AgIO3 precipitate when 20 mL of 0.010 M AgNO3 is mixed with 10 mL of 0.015 M NaIO3? The Ksp of AgIO3 is 3.1 * 10^-8.
Problem 7
Problem 9a
The following graphs represent the behavior of BaCO3 under different circumstances. In each case, the vertical axis indicates the solubility of the BaCO3 and the horizontal axis represents the concentration of some other reagent. (a) Which graph represents what happens to the solubility of BaCO3 as HNO3 is added? [Section 17.5]
Problem 10b
Ca1OH22 has a Ksp of 6.5 * 10-6. (b) If 50 mL of the solution from part (a) is added to each of the beakers shown here, in which beakers, if any, will a precipitate form? In those cases where a precipitate forms, what is its identity? [Section 17.6]
Problem 12
Three cations, Ni2+ , Cu2+ , and Ag+, are separated using two different precipitating agents. Based on Figure 17.23, what two precipitating agents could be used? Using these agents, indicate which of the cations is A, which is B, and which is C.[Section 17.7]
Problem 13
Which of these statements about the common-ion effect is most correct? (a) The solubility of a salt MA is decreased in a solution that already contains either M+ or A-. (b) Common ions alter the equilibrium constant for the reaction of an ionic solid with water. (c) The common-ion effect does not apply to unusual ions like SO32 - . (d) The solubility of a salt MA is affected equally by the addition of either A- or a noncommon ion.
Problem 14c
Consider the equilibrium B1aq2 + H2O1l2 Δ HB+1aq2 + OH-1aq2. Suppose that a salt of HB+1aq2 is added to a solution of B1aq2 at equilibrium. (c) Will the pH of the solution increase, decrease, or stay the same?
- Use information from Appendix D to calculate the pH of (a) a solution that is 0.060 M in potassium propionate (C2H5COOK or KC3H5O2) and 0.085 M in propionic acid (C2H5COOH or HC3H5O2). (b) a solution that is 0.075 M in trimethylamine (CH3)3N and 0.10 M in trimethylammonium chloride (CH3)3NHCl. (c) a solution that is made by mixing 50.0 mL of 0.15 M acetic acid and 50.0 mL of 0.20 M sodium acetate.
Problem 15
- Use information from Appendix D to calculate the pH of: (a) a solution that is 0.250 M in sodium formate (HCOONa) and 0.100 M in formic acid (HCOOH); (b) a solution that is 0.510 M in pyridine (C5H5N) and 0.450 M in pyridinium chloride (C5H5NHCl); (c) a solution that is made by combining 55 mL of 0.050 M hydrofluoric acid with 125 mL of 0.10 M sodium fluoride.
Problem 16
Problem 17a
(a) Calculate the percent ionization of 0.0075 M butanoic acid 1Ka = 1.5 * 10-52.
Problem 17b
(b) Calculate the percent ionization of 0.0075 M butanoic acid in a solution containing 0.085 M sodium butanoate.
Problem 18a
(a) Calculate the percent ionization of 0.125 M lactic acid 1Ka = 1.4 * 10-42.
- Which of the following solutions is a buffer? (a) 0.10 M CH3COOH and 0.10 M CH3COONa, (b) 0.10 M CH3COOH, (c) 0.10 M HCl and 0.10 M NaCl, (d) both a and c, (e) all of a, b, and c.
Problem 19
Problem 20
Which of the following solutions is a buffer? (a) A solution made by mixing 100 mL of 0.100 M CH3COOH and 50 mL of 0.100 M NaOH, (b) a solution made by mixing 100 mL of 0.100 M CH3COOH and 500 mL of 0.100 M NaOH, (c) A solution made by mixing 100 mL of 0.100 M CH3COOH and 50 mL of 0.100 M HCl, (d) A solution made by mixing 100 mL of 0.100 M CH3COOK and 50 mL of 0.100 M KCl.
Problem 21a
(a) Calculate the pH of a buffer that is 0.12 M in lactic acid and 0.11 M in sodium lactate.
- (a) Calculate the pH of a buffer that is 0.105 M in NaHCO3 and 0.125 M in Na2CO3. (b) Calculate the pH of a solution formed by mixing 65 mL of 0.20 M NaHCO3 with 75 mL of 0.15 M Na2CO3.
Problem 22
- A buffer is prepared by adding 20.0 g of sodium acetate (CH3COONa) to 500 mL of a 0.150 M acetic acid (CH3COOH) solution. (b) Write the complete ionic equation for the reaction that occurs when a few drops of hydrochloric acid are added to the buffer. (c) Write the complete ionic equation for the reaction that occurs when a few drops of sodium hydroxide solution are added to the buffer.
Problem 23
- A buffer is prepared by adding 10.0 g of ammonium chloride (NH4Cl) to 250 mL of 1.00 M NH3 solution. (b) Write the complete ionic equation for the reaction that occurs when a few drops of nitric acid are added to the buffer. (c) Write the complete ionic equation for the reaction that occurs when a few drops of potassium hydroxide solution are added to the buffer.
Problem 24
Problem 25a
You are asked to prepare a pH = 3.00 buffer solution starting from 1.25 L of a 1.00 M solution of hydrofluoric acid (HF) and any amount you need of sodium fluoride (NaF). (a) What is the pH of the hydrofluoric acid solution prior to adding sodium fluoride?
Problem 25b
You are asked to prepare a pH = 3.00 buffer solution starting from 1.25 L of a 1.00 M solution of hydrofluoric acid (HF) and any amount you need of sodium fluoride (NaF). (b) How many grams of sodium fluoride should be added to prepare the buffer solution? Neglect the small volume change that occurs when the sodium fluoride is added.
Problem 26a
You are asked to prepare a pH = 4.00 buffer starting from 1.50 L of 0.0200 M solution of benzoic acid 1C6H5COOH2 and any amount you need of sodium benzoate 1C6H5COONa2. (a) What is the pH of the benzoic acid solution prior to adding sodium benzoate?
Problem 26b
You are asked to prepare a pH = 4.00 buffer starting from 1.50 L of 0.0200 M solution of benzoic acid 1C6H5COOH2 and any amount you need of sodium benzoate 1C6H5COONa2. (b) How many grams of sodium benzoate should be added to prepare the buffer? Neglect the small volume change that occurs when the sodium benzoate is added.
