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Prentice Hall Chemistry (c) 2005

Prentice Hall Chemistry (c) 2005. By Daniel R. Barnes Init: 5/5/2010. Section Assessment Answers Chapter 19.

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Prentice Hall Chemistry (c) 2005

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  1. Prentice Hall Chemistry(c) 2005 By Daniel R. Barnes Init: 5/5/2010 Section Assessment Answers Chapter 19 WARNING: some images and content in this presentation may have been taken without permission from the world wide web. It is intended for use only by Mr. Barnes and his students. It is not meant to be copied or distributed. Acids, Bases, & Salts

  2. Reveal all answers 3. What are the properties of acids and bases? Acids and bases are both electrolytes. (They break apart into ions when mixed with water, allowing the resulting solution to conduct electricity.) Acids taste sour, whereas bases taste bitter. pH 8.2 – 12.0 pH 0.0 – 8.2 19.1 Section Assessment Bases feel slippery on your fingers because they turn you into soap. Acids and bases can both affect the color of acid-base “indicator” chemicals, such as phenolphthalein.

  3. Next question please 3. What are the properties of acids and bases? Acids and bases are both electrolytes. (They break apart into ions when mixed with water, allowing the resulting solution to conduct electricity.) Acids taste sour, whereas bases taste bitter. pH 8.2 – 12.0 pH 0.0 – 8.2 19.1 Section Assessment Bases feel slippery on your fingers because they turn you into soap. Acids and bases can both affect the color of acid-base “indicator” chemicals, such as phenolphthalein.

  4. Reveal all answers 4. How did Arrhenius define an acid and a base? In aqueous solutions . . . H+ An acid gives hydrogen ions. H2O OH- An base gives hydroxide ions. 19.1 Section Assessment HCl is an Arrhenius ACID. HCl + H2O  H3O+ + Cl- NaOH is an Arrhenius BASE. NaOH  Na+ + OH-

  5. Next question please 4. How did Arrhenius define an acid and a base? In aqueous solutions . . . H+ An acid gives hydrogen ions. H2O OH- An base gives hydroxide ions. 19.1 Section Assessment HCl is an Arrhenius ACID. HCl + H2O  H3O+ + Cl- NaOH is an Arrhenius BASE. NaOH  Na+ + OH-

  6. Reveal all answers 5. How are acids and bases defined by the Bronsted-Lowry theory? (proton donors) Acids are hydrogen ion givers. (proton acceptors) Bases are hydrogen ion takers. 19.1 Section Assessment NH3 is a Bronsted-Lowry BASE. NH3 + H2O  NH4+ + OH- Lookie! By accepting a proton, NH3 ended up indirectly creating an OH- anyway!

  7. Next question please 5. How are acids and bases defined by the Bronsted-Lowry theory? (proton donors) Acids are hydrogen ion givers. (proton acceptors) Bases are hydrogen ion takers. 19.1 Section Assessment NH3 is a Bronsted-Lowry BASE. NH3 + H2O  NH4+ + OH- Lookie! By accepting a proton, NH3 ended up indirectly creating an OH- anyway!

  8. Reveal all answers 6. What is the Lewis theory of acids and bases? A Lewis “acid” is any substance that can accept an electron pair to form a covalent bond. A Lewis “base” is any substance that can donate an electron pair to form a covalent bond. 19.1 Section Assessment

  9. Next question please 6. What is the Lewis theory of acids and bases? A Lewis “acid” is any substance that can accept an electron pair to form a covalent bond. A Lewis “base” is any substance that can donate an electron pair to form a covalent bond. 19.1 Section Assessment

  10. Reveal all answers 7.a. What is a conjugate acid-base pair? A conjugate acid-base pair is a pair of substances related by the loss or gain of a single hydrogen ion. The conjugate base of an acid is what’s left of an acid molecule after it gives up the hydrogen ion. The conjugate acid of a base is what a base molecule has become after it receives a hydrogen ion. 19.1 Section Assessment NH3 + H2O  NH4+ + OH- BASE ACID ACID BASE NH4+ is the conjugate acid of NH3. OH- is the conjugate base of H2O.

  11. Next question please 7.a. What is a conjugate acid-base pair? A conjugate acid-base pair is a pair of substances related by the loss or gain of a single hydrogen ion. The conjugate base of an acid is what’s left of an acid molecule after it gives up the hydrogen ion. The conjugate acid of a base is what a base molecule has become after it receives a hydrogen ion. 19.1 Section Assessment NH3 + H2O  NH4+ + OH- BASE ACID ACID BASE NH4+ is the conjugate acid of NH3. OH- is the conjugate base of H2O.

  12. Reveal all answers 7.b. Write equations for the ionization of HNO3 in water and the reaction of CO32- with water. For each equation, identify the hydrogen-ion donor and the hydrogen-ion donor. Then label the conjugate acid-base pairs in each equation. HNO3 + H2O  H3O+ + NO3- 19.1 Section Assessment HNO3 is the hydrogen ion donor. HNO3’s conjugate base is NO3-. (It’s what HNO3 turns into when it donates a proton.) H2O is the hydrogen ion acceptor. H2O’s conjugate acid is H3O+. (It’s what H2O turns into when it accepts a proton.)

  13. Next question please 7.b. Write equations for the ionization of HNO3 in water and the reaction of CO32- with water. For each equation, identify the hydrogen-ion donor and the hydrogen-ion donor. Then label the conjugate acid-base pairs in each equation. HNO3 + H2O  H3O+ + NO3- 19.1 Section Assessment HNO3 is the hydrogen ion donor. HNO3’s conjugate base is NO3-. (It’s what HNO3 turns into when it donates a proton.) H2O is the hydrogen ion acceptor. H2O’s conjugate acid is H3O+. (It’s what H2O turns into when it accepts a proton.)

  14. Reveal all answers 7.b. Write equations for the ionization of HNO3 in water and the reaction of CO32- with water. For each equation, identify the hydrogen-ion donor and the hydrogen-ion donor. Then label the conjugate acid-base pairs in each equation. CO32- + H2O  HCO3- + OH- 19.1 Section Assessment CO32- is the hydrogen ion acceptor. CO32-’s conjugate acid is HCO3-. (It’s what CO32- turns into when it accepts a proton.) H2O is the hydrogen ion donor. H2O’s conjugate base is OH-. (It’s what H2O turns into when it donates a proton.)

  15. Next question please 7.b. Write equations for the ionization of HNO3 in water and the reaction of CO32- with water. For each equation, identify the hydrogen-ion donor and the hydrogen-ion donor. Then label the conjugate acid-base pairs in each equation. CO32- + H2O  HCO3- + OH- 19.1 Section Assessment CO32- is the hydrogen ion acceptor. CO32-’s conjugate acid is HCO3-. (It’s what CO32- turns into when it accepts a proton.) H2O is the hydrogen ion donor. H2O’s conjugate base is OH-. (It’s what H2O turns into when it donates a proton.)

  16. Reveal all answers 8.b. Identify the following acids as monoprotic, diprotic, or triprotic. Explain your reasoning. a. H2CO3 = diprotic because it can give off two H+’s. b. H3PO4 = triprotic because it can give off three H+’s. c. HCl = monoprotic because it can give off one H+. 19.1 Section Assessment d. H2SO4 = diprotic because it can give off two H+’s.

  17. Next question please 8.b. Identify the following acids as monoprotic, diprotic, or triprotic. Explain your reasoning. a. H2CO3 = diprotic because it can give off two H+’s. b. H3PO4 = triprotic because it can give off three H+’s. c. HCl = monoprotic because it can give off one H+. 19.1 Section Assessment d. H2SO4 = diprotic because it can give off two H+’s.

  18. Reveal all answers 17. What is the relationship between [H+] and [OH-] in an aqueous solution? [H+] x [OH-] = 1.0 x 10-14; when [H+] in a solution increases, the [OH-] decreases. 19.2 Section Assessment

  19. Next question please 17. What is the relationship between [H+] and [OH-] in an aqueous solution? [H+] x [OH-] = 1.0 x 10-14; when [H+] in a solution increases, the [OH-] decreases. 19.2 Section Assessment

  20. Reveal all answers 18. What is true about the relative concentrations of hydrogen ions and hydroxide ions in each kind of solution? Hydroxide ion concentration is greater. a. basic . . . Hydrogen ion concentration is greater. b. acidic . . . The concentrations are equal. c. neutral . . . 19.2 Section Assessment

  21. Next question please 18. What is true about the relative concentrations of hydrogen ions and hydroxide ions in each kind of solution? Hydroxide ion concentration is greater. a. basic . . . Hydrogen ion concentration is greater. b. acidic . . . The concentrations are equal. c. neutral . . . 19.2 Section Assessment

  22. Reveal all answers 19. What is true about the colors of a pH indicator? The color of HIn(aq) must be different than the color of In-(aq). 19.2 Section Assessment

  23. Next question please 19. What is true about the colors of a pH indicator? The color of HIn(aq) must be different than the color of In-(aq). 19.2 Section Assessment

  24. Reveal all answers 20. Determine the pH of each solution. a. [H+] = 1 x 10-6M . . . pH = 6 b. [H+] = 0.00010 M. . . pH = 4 c. [OH-] = 1 x 10-2M. . . pH = 12 d. [OH-] = 1 x 10-11M. . . pH = 3 19.2 Section Assessment

  25. Next question please 20. Determine the pH of each solution. a. [H+] = 1 x 10-6M . . . pH = 6 b. [H+] = 0.00010 M. . . pH = 4 c. [OH-] = 1 x 10-2M. . . pH = 12 d. [OH-] = 1 x 10-11M. . . pH = 3 19.2 Section Assessment

  26. Reveal all answers 21. What are the hydroxide ion concentrations for solutions with the following pH values? a. If pH = 6, [OH-] = 1 x 10-8 M b. If pH = 9, [OH-] = 1 x 10-5 M c. If pH = 12, [OH-] = 1 x 10-2 M 19.2 Section Assessment

  27. Next question please 21. What are the hydroxide ion concentrations for solutions with the following pH values? a. If pH = 6, [OH-] = 1 x 10-8 M b. If pH = 9, [OH-] = 1 x 10-5 M c. If pH = 12, [OH-] = 1 x 10-2 M 19.2 Section Assessment

  28. Reveal all answers 24. Compare a strong acid and a weak acid in terms of the acid dissociation constant. A strong acid is completely ionized in aqeuous solution and has a large Ka. A weak acid is ionized only slightly in aqueous solution and has a small Ka. 19.3 Section Assessment

  29. Next question please 24. Compare a strong acid and a weak acid in terms of the acid dissociation constant. A strong acid is completely ionized in aqeuous solution and has a large Ka. A weak acid is ionized only slightly in aqueous solution and has a small Ka. 19.3 Section Assessment

  30. Reveal all answers 25. How do you determine the Ka of a weak acid or the Kb of a weak base? Substitute the measured concentrations of all the substances present at equilibrium into the expressions for Ka or Kb. 19.3 Section Assessment

  31. Next question please 25. How do you determine the Ka of a weak acid or the Kb of a weak base? Substitute the measured concentrations of all the substances present at equilibrium into the expressions for Ka or Kb. 19.3 Section Assessment

  32. Reveal all answers • Which acid in Table 19.6 would you expect to have the lowest ionization constant? hypochlorous acid 19.3 Section Assessment

  33. Next question please • Which acid in Table 19.6 would you expect to have the lowest ionization constant? hypochlorous acid 19.3 Section Assessment

  34. Reveal all answers 27. Acid HX has a very small value of Ka. How do the relative amounts of H+ and HX compare at equilibrium? [HX] is much greater than [H+]. 19.3 Section Assessment

  35. Next question please 27. Acid HX has a very small value of Ka. How do the relative amounts of H+ and HX compare at equilibrium? [HX] is much greater than [H+]. 19.3 Section Assessment

  36. Reveal all answers 28. Write the equations for the ionization or dissociation of the following acids and bases in water. a. nitric acid: HNO3 + H2O  H3O+ + NO3- b. ethanoic acid: CH3COOH + H2O  CH3COO- + H3O+ c. ammonia: NH3 + H2O  NH4+ + OH- d. magnesium hydroxide: Mg(OH)2 Mg2+ + 2OH- 19.3 Section Assessment

  37. Next question please 28. Write the equations for the ionization or dissociation of the following acids and bases in water. a. nitric acid: HNO3 + H2O  H3O+ + NO3- b. ethanoic acid: CH3COOH + H2O  CH3COO- + H3O+ c. ammonia: NH3 + H2O  NH4+ + OH- d. magnesium hydroxide: Mg(OH)2 Mg2+ + 2OH- 19.3 Section Assessment

  38. Reveal all answers 29. Compare the terms strong/weak and concentrated/dilute as they pertain to acids and bases. “Strong acids and bases are completely ionized in aqeous solution. Weak acids and bases ionize only slightly in aqueous solution. Concentrated acid or base solutions contain large amounts of acid or base. Dilute acid or base solutions contain small amounts (low concentrations) of acid or base.” 19.3 Section Assessment Strong vs weak has nothing to do with amount of water added. Concentrated vs. dilute is based pretty much entirely on how much water is mixed with the acid or base.

  39. Next question please 29. Compare the terms strong/weak and concentrated/dilute as they pertain to acids and bases. “Strong acids and bases are completely ionized in aqeous solution. Weak acids and bases ionize only slightly in aqueous solution. Concentrated acid or base solutions contain large amounts of acid or base. Dilute acid or base solutions contain small amounts (low concentrations) of acid or base.” 19.3 Section Assessment Strong vs weak has nothing to do with amount of water added. Concentrated vs. dilute is based pretty much entirely on how much water is mixed with the acid or base.

  40. Reveal all answers 34. What are the products of a reaction between an acid and a base? “a salt and water” The salt produced is not always NaCl, but water is always H2O. 19.4 Section Assessment

  41. Next question please 34. What are the products of a reaction between an acid and a base? “a salt and water” The salt produced is not always NaCl, but water is always H2O. 19.4 Section Assessment

  42. Reveal all answers 35. What occurs at the endpoint of a titration? neutralization 19.4 Section Assessment

  43. Next question please 35. What occurs at the endpoint of a titration? neutralization 19.4 Section Assessment

  44. Reveal all answers 36. How many moles of HCl are required to neutralize aqueous solutions of these bases? a. 2 mol NH3 . . . requires 2 mol HCl to be neutralized. a. 0.1 mol Ca(OH)2 . . . requires 0.2 mol HCl to be neutralized. 19.4 Section Assessment

  45. Next question please 36. How many moles of HCl are required to neutralize aqueous solutions of these bases? a. 2 mol NH3 . . . requires 2 mol HCl to be neutralized. a. 0.1 mol Ca(OH)2 . . . requires 0.2 mol HCl to be neutralized. 19.4 Section Assessment

  46. Reveal all answers 37. Write complete balanced equations for the following acid-base reactions. 2 a. H2SO4(aq) + KOH(aq)  + H2O + K2SO4 2 3 b. H3PO4(aq) + Ca(OH)2(aq)  H2O + Ca3(PO4)2 6 2 2 c. HNO3(aq) + Mg(OH)2(aq)  H2O + Mg(NO3)2 2 19.4 Section Assessment

  47. Next question please 37. Write complete balanced equations for the following acid-base reactions. 2 a. H2SO4(aq) + KOH(aq)  + H2O + K2SO4 2 3 b. H3PO4(aq) + Ca(OH)2(aq)  H2O + Ca3(PO4)2 6 2 2 c. HNO3(aq) + Mg(OH)2(aq)  H2O + Mg(NO3)2 2 19.4 Section Assessment

  48. Reveal all answers 40. What type of salt produces an acidic solution? A basic solution? “A salt of a strong acid and a weak base produces an acidic solution.” “A salt of a strong base and a weak acid produces a basic solution.” 19.5 Section Assessment A salt of a strong acid and a strong base produces a neutral solution. A salt of a weak acid and a weak base will produce an acidic solution if the acid is stronger than the base, and a basic solution if the base is stronger than the acid.

  49. Next question please 40. What type of salt produces an acidic solution? A basic solution? “A salt of a strong acid and a weak base produces an acidic solution.” “A salt of a strong base and a weak acid produces a basic solution.” 19.5 Section Assessment A salt of a strong acid and a strong base produces a neutral solution. A salt of a weak acid and a weak base will produce an acidic solution if the acid is stronger than the base, and a basic solution if the base is stronger than the acid.

  50. Reveal all answers 41. What substances are combined to make a buffer? a weak acid and one of its salts or a weak base and one of its salts 19.5 Section Assessment

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