8. Our bodies are able to preserve a near constant pH due to the presence of hydrogen carbonate anion (HCO;"). K values for the diprotic acid carbonic acid (H;CO;) are Kj = 4.5 x 107, K2 = 4.7 x 10-1". a) Hydrogen carbonate anion is an amphoteric species. Define amphoteric. b) In the space below, write out chemical equations to describe the behavior of this species as both a Bronsted acid and a Bronsted base, and use the equilibrium constants given above to decipher whether a solution of HCO;, will be acidic, basic, or neutral. Support your answer with pertinent calculations.

8. Our bodies are able to preserve a near constant pH due to the presence of hydrogen carbonate anion (HCO;"). K values for the diprotic acid carbonic acid (H;CO;) are Kj = 4.5 x 107, K2 = 4.7 x 10-1". a) Hydrogen carbonate anion is an amphoteric species. Define amphoteric. b) In the space below, write out chemical equations to describe the behavior of this species as both a Bronsted acid and a Bronsted base, and use the equilibrium constants given above to decipher whether a solution of HCO;, will be acidic, basic, or neutral. Support your answer with pertinent calculations.

Chemistry

10th Edition

ISBN:9781305957404

Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste

Chapter14: Acids And Bases

Section: Chapter Questions

Problem 7RQ: Table 13-4 lists the stepwise Ka values for some polyprotic acids. What is the difference between a...

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Strong Acids, Weak Acids, and pH Two 0.10-mol samples of the hypothetical monoprotic acids HA(aq) and HB(aq) are used to prepare 1.0-L stock solutions of each acid. a Write the chemical reactions for these acids in water. What are the concentrations of the two acid solutions? b One of these acids is a strong acid, and one is weak. What could you measure that would tell you which acid was strong and which was weak? c Say that the HA(aq) solution has a pH of 3.7. Is this the stronger of the two acids? How did you arrive at your answer? d What is the concentration of A(aq) in the HA solution described in part c? e If HB(aq) is a strong acid, what is the hydronium-ion concentration? f In the solution of HB(aq), which of the following would you expect to be in the greatest concentration: H3O+(aq), B(aq), HB(aq), or OH(aq)? How did you decide? g In the solution of HA(aq), which of the following would you expect to be in the greatest concentration: H3O+(aq), A+(aq), HA(aq), or OH(aq)? How did you decide? h Say you add 1.0 L of pure water to a solution of HB. Would this water addition make the solution more acidic, make it less acidic, or not change the acidity of the original solution? Be sure to fully justify your answer. i You prepare a 1.0-L solution of HA. You then take a 200-mL sample of this solution and place it into a separate container. Would this 200 mL sample be more acidic, be less acidic, or have the same acidity as the original 1.0-L solution of HA(aq)? Be sure to support your answer.
What is a salt? List some anions that behave as weak bases in water. List some anions that have no basic properties in water. List some cations that behave as weak acids in water. List some cations that have no acidic properties in water. Using these lists, give some formulas for salts that have only weak base properties in water. What strategy would you use to solve for the pH of these basic salt solutions? Identify some salts that have only weak acid properties in water. What strategy would you use to solve for the pH of these acidic salt solutions? Identify some salts that have no acidic or basic properties in water (produce neutral solutions). When a salt contains both a weak acid ion and a weak base ion, how do you predict whether the solution pH is acidic, basic, or neutral?
. The concepts of acid-base equilibria were developed in this chapter for aqueous solutions (in aqueous solutions, water is the solvent and is intimately involved in the equilibria). However, the Brønsted-Lowry acid-base theory can be extended easily to other solvents. One such solvent that has been investigated in depth is liquid ammonia. NH3. a. Write a chemical equation indicating how HCl behaves as an acid in liquid ammonia. b. Write a chemical equation indicating how OH- behaves as a base in liquid ammonia.
Table 13-4 lists the stepwise Ka values for some polyprotic acids. What is the difference between a monoprotic acid, a diprotic acid, and a triprotic acid? Most polyprotic acids are weak acids; the major exception is H2SO4. To solve for the pH of a solution of H2SO4, you must generally solve a strong acid problem as well as a weak acid problem. Explain. Write out the reactions that refer to Ka1 and Ka2 for H2SO4. For H3PO4, Ka1 = 7.5 103, Ka2 = 6.2 108, and Ka3= 4.8 1013. Write out the reactions that refer to the Ka1, Ka2and Ka3equilibrium constants. What are the three acids in a solution of H3PO4? Which acid is strongest? What are the three conjugate bases in a solution of H3PO4? Which conjugate base is strongest? Summarize the strategy for calculating the pH of a polyprotic acid in water.
Consider a solution prepared by mixing a weak acid HA. HCl, and NaA. Which of the following statements best describes what happens? a. The H+ from the HCl reacts completely with the A from the NaA. Then the HA dissociates somewhat. b. The H+ from the HCl reacts somewhat with the A from the NaA to make HA, while the HA is dissociating. Eventually you have equal amounts of everything. c. The H+ from the HCl reacts somewhat with the A from the NaA to make HA while the HA is dissociating. Eventually all the reactions have equal rates. d. The H+ from the HCl reacts completely with the A from the NaA. Then the HA dissociates somewhat until too much H+ and A are formed, so the H+ and A react to form HA, and so on. Eventually equilibrium is reached. Justify your choice, and for choices you did not pick, explain what is wrong with them.
You have a solution of the weak acid HA and add some HCl to it. What are the major species in the solution? What do you need to know to calculate the pH of the solution, and how would you use this information? How does the pH of the solution of just the HA compare with that of the final mixture? Explain.
Write the Lewis structures of the reactants and product of each of the following equations, and identify the Lewis acid and the Lewis base in each: (a) CS2+SHHCS3 (b) BF3+FBF4 (c) I+SnI2SnI3 (d) Al(OH)3+OHAl(OH)4 (e) F+SO3SFO3
A solution is prepared from 0.150 mol of formic acid and enough water to make 0.425 L of solution. a Determine the concentrations of H3O+ and HCOO in this solution. b Determine the H3O+ concentration that would be necessary to decrease the HCOO concentration above by a factor of 10. How many milliliters of 2.00 M HCl would be required to produce this solution? Consider that the solution was made by combining the HCl, the HCOOH, and enough water to make 0.425 L of solution. c Qualitatively, how can you account for the differences in the percentage dissociation of formic acid in parts a and b of this problem?
A friend asks the following: Consider a buffered solution made up of the weak acid HA and its salt NaA. If a strong base like NaOH is added, the HA reacts with the OH to form A. Thus the amount of acid (HA) is decreased, and the amount of base (A) is increased. Analogously, adding HCI to the buffered solution forms more of the acid (HA) by reacting with the base (A). Thus how can we claim that a buffered solution resists changes in the pH of the solution? How would you explain buffering to this friend?
Malic 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?
Ionization 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.

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