Concept explainers
Tooth enamel is largely hydroxyapatite [Ca3(PO4)3OH]. When it dissolves in water (a process called demineralization), it dissociates as follows:
The reverse process, called remineralization, is the body’s natural defense against tooth decay. Acids produced from food remove the OH− ions and thereby weaken the enamel layer. Most toothpastes contain a fluoride compound such as NaF or SnF2. What is the function of these compounds in preventing tooth decay?
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Chapter 16 Solutions
Chemistry: Atoms First
- Write an equation for each of the following buffering actions. a. the response of a HPO42/PO43 buffer to the addition of OH ions b. the response of a HF/F buffer to the addition of OH ions c. the response of a HCN/CN buffer to the addition of H3O+ ions d. the response of a H3PO4/H2PO4 buffer to the addition of H3O+ ionsarrow_forwardTartaric acid is a weak diprotic fruit acid with Ka1 = 1.0 103 and Ka2 = 4.6 105. a Letting the symbol H2A represent tartaric acid, write the chemical equations that represent Ka1 and Ka2. Write the chemical equation that represents Ka1 Ka2. b Qualitatively describe the relative concentrations of H2A, HA, A2, and H3O+ in a solution that is about 0.5 M in tartaric acid. c Calculate the pH of a 0 0250 M tartaric acid solution and the equilibrium concentration of [H2A]. d What is the A2 concentration in solutions b and c?arrow_forwardIonization of the first proton from H2SO4 is complete (H2SO4 is a strong acid); the acid-ionization constant for the second proton is 1.1 102. a What would be the approximate hydronium-ion concentration in 0.100 M H2SO4 if ionization of the second proton were ignored? b The ionization of the second proton must be considered for a more exact answer, however. Calculate the hydronium-ion concentration in 0.100 M H2SO4, accounting for the ionization of both protons.arrow_forward
- In the following reaction of tetrafluoroboric acid, HBF4, with the acetate ion, C2H3O2, the formation of tetrafluoroborate ion, BF4 , and acetic acid, HC2H3O2 is favored. HBF4+C2H3O2BF4+HC2H3O2 Which is the weaker base, BF4 or acetate ion?arrow_forwardMalic acid is a weak diprotic organic acid with Ka1 = 4.0 104 and Ka2 = 9.0 105. a Letting the symbol H2A represent malic acid, write the chemical equations that represent Ka1 and Ka2. Write the chemical equation that represents Ka1 Ka2. b Qualitatively describe the relative concentrations of H2A, HA, A2, and H3O+ in a solution that is about one molar in malic acid. c Calculate the pH of a 0.0175 M malic acid solution and the equilibrium concentration of [H2A]. d What is the A2 concentrationin in solutions b and c?arrow_forwardConsider all acid-base indicators discussed in this chapter. Which of these indicators would be suitable for the titration of each of these? (a) NaOH with HClO4 (b) acetic acid with KOH (c) NH3 solution with HBr (d) KOH with HNO3 Explain your choices.arrow_forward
- Estimate the pH that results when the following two solutions are mixed. a) 50 mL of 0.3 M CH3COOH and 50 mL of 0.4 M KOH b) 100 mL of 0.3 M CH3COOH and 50 mL of 0.4 M NaOH c) 150 mL of 0.3 M CH3COOH and 100 mL of 0.3 M Ba(OH)2 d) 200 mL of 0.3 M CH3COOH and 100 mL of 0.3 M Ba(OH)2arrow_forwardTwo strategies are also followed when solving for the pH of a base in water. What is the strategy for calculating the pH of a strong base in water? List the strong bases mentioned in the text that should be committed to memory. Why is calculating the pH of Ca(OH)2 solutions a little more difficult than calculating the pH of NaOH solutions? Most bases are weak bases. The presence of what element most commonly results in basic properties for an organic compound? What is present on this element in compounds that allows it to accept a proton? Table 13-3 and Appendix 5 of the text list Kb values for some weak bases. What strategy is used to solve for the pH of a weak base in water? What assumptions are made when solving for the pH of weak base solutions? If the 5% rule fails, how do you calculate the pH of a weak base in water?arrow_forwardThe pH of Mixtures of Acid, Base, and Salt Solutions a When 0.10 mol of the ionic solid NaX, where X is an unknown anion, is dissolved in enough water to make 1.0 L of solution, the pH of the solution is 9.12. When 0.10 mol of the ionic solid ACl, where A is an unknown cation, is dissolved in enough water to make 1.0 L of solution, the pH of the solution is 7.00. What would be the pH of 1.0 L of solution that contained 0.10 mol of AX? Be sure to document how you arrived at your answer. b In the AX solution prepared above, is there any OH present? If so, compare the [OH] in the solution to the [H3O+]. c From the information presented in part a, calculate Kb for the X(aq) anion and Ka for the conjugate acid of X(aq). d To 1.0 L of solution that contains 0.10 mol of AX, you add 0.025 mol of HCl. How will the pH of this solution compare to that of the solution that contained only NaX? Use chemical reactions as part of your explanation; you do not need to solve for a numerical answer. e Another 1.0 L sample of solution is prepared by mixing 0.10 mol of AX and 0.10 mol of HCl. The pH of the resulting solution is found to be 3.12. Explain why the pH of this solution is 3.12. f Finally, consider a different 1.0-L sample of solution that contains 0.10 mol of AX and 0.1 mol of NaOH. The pH of this solution is found to be 13.00. Explain why the pH of this solution is 13.00. g Some students mistakenly think that a solution that contains 0.10 mol of AX and 0.10 mol of HCl should have a pH of 1.00. Can you come up with a reason why students have this misconception? Write an approach that you would use to help these students understand what they are doing wrong.arrow_forward
- Given the acid-base indicators in Question 37, select a suitable indicator for the following titrations. (a) sodium formate (NaCHO2) with HNO3 (b) hypochlorous acid with barium hydroxide (c) nitric acid with HI (d) hydrochloric acid with ammoniaarrow_forwardWhat is the pH of a solution obtained by adding 13.0 g of NaOH to 795 mL of a 0.200 M solution of Sr(OH)2? Assume no volume change after NaOH is added.arrow_forwardHydrogen sulfide, H2S, is a very weak diprotic acid. In a 0.10 M solution of this acid, which of the following would you expect to find in the highest concentration? a H2S b H3O+ c HS d S2 e OHarrow_forward
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