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  CHAPTER 14 Acids and Bases 321 © Houghton Mifflin Company. All rights reserved.   1. For the equilibrium that exists in an aqueous solution of nitrous acid (HNO 2 , a weak acid), the equilibrium constant expression is: a) K   = [H + ][NO 2– ][HNO 2 ] b) K   = [H + ][N][O] 2 [HNO 2 ] c) K   = [H + ][NO 2– ] d) K   = [H + ] 2 [NO 2– ][HNO 2 ] e) none of these ANS:  a) K   = [H + ][NO 2– ][HNO 2 ]  PAGE:  14.1 2. Which of the following is a conjugate acid/base pair? a) HCl/OCl -  b) H 2 SO 4 /SO 42-  c) NH 4+ /NH 3  d) H 3 O + /OH -  e) none of these ANS:  c) NH 4+ /NH 3   PAGE:  14.1 3. The equilibrium constant for the reaction A –  + H +  HA is called: a) K  a  b) K  b  c) 1 K  a  d) K  w K  b  e) K  w K  a   ANS:  c) 1 K  a   PAGE:  14.1  CHAPTER 14 Acids and Bases 322 © Houghton Mifflin Company. All rights reserved.   4. For the stepwise dissociation of aqueous H 3 PO 4 , which of the following is not a conjugate acid–base pair? a) HPO 42–  and PO 43–  b) H 3 PO 4  and H 2 PO 4–  c) H 2 PO 4–  and HPO 42–  d) H 2 PO 4– and PO 43–  e) H 3 O +  and H 2 O ANS:  d) H 2 PO 4–  and PO 43–   PAGE:  14.1,7 5. What is the equilibrium constant for the following reaction? N 3–  + H 3 O +  HN 3 + H 2 O The K  a  value for HN 3  = 1.9 ×  10 –5 . a) 5.3 ×  10 –10  b) 1.9 ×  10 –9  c) 1.9 ×  10 –5  d) 5.3 ×  10 4  e) 1.9 ×  10 9   ANS:  d) 5.3 ×  10 4   PAGE:  14.1 6. The hydrogen sulfate or bisulfate ion HSO 4–  can act as either an acid or a base in water solution. In which of the following equations does HSO 4–  act as an acid? a) HSO 4–  + H 2 O →  H 2 SO 4  + OH –  b) HSO 4–  + H 3 O +   →  SO 3  + 2H 2 O c) HSO 4–  + OH –   →  H 2 SO 4  + O 2–  d) HSO 4–  + H 2 O →  SO 42–  + H 3 O +  e) none of these ANS:  d) HSO 4–  + H 2 O →  SO 42–  + H 3 O +   PAGE:  14.1,2  CHAPTER 14 Acids and Bases © Houghton Mifflin Company. All rights reserved.  323 7. Using the following K  a  values, indicate the correct order of base strength. HNO 2   K  a  = 4.0 ×  10 –4  HF K  a  = 7.2 ×  10 –4  HCN K  a  = 6.2 ×  10 –10  a) CN –  > NO 2–  > F –  > H 2 O > Cl –  b) Cl –  > H 2 O > F – > NO 2–  > CN –  c) CN –  > F –  > NO 2–  > Cl –  > H 2 O d) H 2 O > CN –  > NO 2–  > F –  > Cl –  e) none of these ANS:  a) CN –  > NO 2–  > F –  > H 2 O > Cl –   PAGE:  14.2 8. At 0°C, the ion-product constant of water, K  w , is 1.2 ×  10 –15 . The pH of pure water at 0°C is: a) 7.00 b) 6.88 c) 7.56 d) 7.46 e) none of these ANS:  d) 7.46 PAGE:  14.2,3 9. The equilibrium constants ( K  a ) for HCN and HF in H 2 O at 25°C are 6.2 ×  10 –10  and 7.2 ×  10 –4 , respectively. The relative order of base strengths is: a) F –  > H 2 O > CN –  b) H 2 O > F –  > CN –  c) CN –  > F –  > H 2 O d) F –  > CN –  > H 2 O e) none of these ANS:  c) CN –  > F –  > H 2 O PAGE:  14.2  CHAPTER 14 Acids and Bases 324 © Houghton Mifflin Company. All rights reserved.   10. Given the following acids and K  a values: HClO 4  HOAc HCN HF 1 ×  10 7  1.76 ×  10 –5  4.93 ×  10 –10  3.53 ×  10 –4  which shows the conjugate bases listed by increasing strength? a) CN – , F – , OAc – , ClO 4–  b) CN – , OAc – , F – , ClO 4–  c) CN – , ClO 4– , F – , OAc –  d) ClO 4– , OAc – , CN – , F –  e) ClO 4– , F – , OAc – , CN –   ANS:  e) ClO 4– , F – , OAc – , CN –   PAGE:  14.2 11. The conjugate base of a weak acid is a) a strong base b) a weak base c) a strong acid d) a weak acid e) none of these ANS:  b) a weak base PAGE:  14.2 12. Which of the following is the equilibrium constant expression for the dissociation of the weak acid HOCl? a) K   = [H + ][OCl – ][HOCl] b) K   = [H + ][OCl – ] c) K   = [HOCl][H + ][OCl – ] d) K   = [H + ][O 2– ][Cl – ][HOCl] e) none of these ANS:  a) K   = [H + ][OCl – ][HOCl]  PAGE:  14.1,2 13–14. The following three equations represent equilibria that lie far to the right. HNO 3 (aq) + CN – (aq) HCN(aq) + NO 3– (aq) HCN(aq) + OH – (aq) H 2 O(l) + CN – (aq) H 2 O(l) + CH 3 O – (aq) CH 2 OH(aq) + OH – (aq)
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