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Chapter 16 Acid-Base Equilibria

Chapter 16 Acid-Base Equilibria. Chemistry, The Central Science, 10th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten. Troy Wood University of Buffalo Buffalo, NY  2006, Prentice Hall. Is NH 3 an acid, base, or could it be both?. Acid Base Both. Correct Answer:.

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Chapter 16 Acid-Base Equilibria

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  1. Chapter 16Acid-Base Equilibria Chemistry, The Central Science, 10th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten Troy Wood University of Buffalo Buffalo, NY  2006, Prentice Hall

  2. Is NH3an acid, base, or could it be both? Acid Base Both

  3. Correct Answer: Acid Base Both In this chapter we learned that a more general definition for a base is a substance that can accept another proton, which is true for NH3 because of the lone electron pair on the N atom.

  4. Is H2O an acid, base, or could it be both? Acid Base Both

  5. Correct Answer: Acid Base Both As indicated in the equilibrium below, water is an amphoteric substance that can either accept another proton or donate a proton.

  6. - - O O + - - - - O P O O P O - O O Is the ion PO43an acid, base, or could it be both? Acid Base Both

  7. - - O O + - - - - O P O O P O - O O Correct Answer: Acid Base Both Phosphate is a proton acceptor, regardless of which resonance structure is being considered.

  8. What is the approximate pH of an aqueous solution of 1  1012M HCl? 2 7 12 14 None of the above

  9. Correct Answer: 2 7 12 14 None of the above This is an aqueous solution, therefore water will autoionize. The concentration of protons due to autoionization of water will dominate that of such a dilute strong acid.

  10. What is [H+] in an aqueous solution whose pH = 3.72? 1.9  103M 5.1  103M 1.9  104M 5.1  104M 5.1  1010M

  11. Correct Answer: 1.9  103M 5.1  103M 1.9  104M 5.1  104M 5.1  1010M 3.72 = log[H+] 3.72 = log[H+] [H+] = 1.9  104 M

  12. What is the pH of an aqueous solution of [OH] = 6.0  103M? 2.22 3.22 7.00 10.78 11.78

  13. Correct Answer: 2.22 3.22 7.00 10.78 11.78 There is more than one method to solve this problem. One is presented below: pOH = log(6.0  103) = 2.22 pH = 14.00  pOH = 14.00  2.22 = 11.78

  14. The [H+] in an 0.020 M solution of HNO2 is 3.0  103M. What is the Ka of HNO2? 4.5  104 6.0  105 9.0  106 1.5  101 None of the above

  15. Correct Answer: • 4.5  104 • 6.0  105 • 9.0  106 • 1.5  101 • None of the above - -   3 2 6 [3.0 10 ] 9.0 10 = = K a 0.020 0.020 - =  4 K 4.5 10 a

  16. The pH of a 0.050 M weak acid is 3.00. What is the percentage ionization? 0.10% 0.20% 1.0% 2.0% 3.0%

  17. Correct Answer: Since pH = 3.00, [H+] = 1.0  103M, so 0.10% 0.20% 1.0% 2.0% 3.0% + [H ] eq =  % ionization 100% [HA] o  -3 [1.0 10 ] =  % ionization 100% [0.050]

  18. For a certain weak acid, Ka = 2.0  105. What is Kb for its conjugate base? 4.5  103 5.0  103 1.0  109 4.0  1010 5.0  1010

  19. Correct Answer: 4.5  103 5.0  103 1.0  109 4.0  1010 5.0  1010 = K K K a b w [ ]  -14 1.0 10 - = =  10 K 5.0 10 ] [ b  - 5 2.0 10

  20. Which of the following oxyacid species is the strongest acid? HClO HClO2 HClO3 HClO4

  21. Correct Answer: HClO HClO2 HClO3 HClO4 For oxyacids that have the same central atom Y, acid strength increases as the number of O atoms bound to Y increases. Thus, HClO4 is the strongest acid of this series.

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