Chem 1120: Chapter 17

The highest pH for an effective buffer occurs when the base is how many times as concentrated as the acid? a) 10 b) 40 c) 8 d) 5 e) 25

a) 10

Which of the following solutions is a good buffer system? a) A solution that is 0.10 M HC₂H₃O₂ and 0.10 M LiC₂H₃O₂ b) A solution that is 0.10 M HI and 0.10 M NH₄⁺ c) A solution that is 0.10 M HBr and 0.10 M KC₂H₃O₂ d) A solution that is 0.10 M NaOH and 0.10 M KOH e) None of the above are buffer systems.

a) A solution that is 0.10 M HC₂H₃O₂ and 0.10 M LiC₂H₃O₂

Which of the following is TRUE? a) The equivalence point is where the amount of acid equals the amount of base during any acid-base titration. b) An indicator is not pH sensitive. c) At the equivalence point, the pH is always 7. d) A titration curve is a plot of pH vs. the [base]/[acid] ratio. e) None of the above are true.

a) The equivalence point is where the amount of acid equals the amount of base during any acid-base titration.

Which of the following is TRUE? a) A buffer can not be destroyed by adding too much strong base. It can only be destroyed by adding too much strong acid. b) A buffer is most resistant to pH change when [acid] = [conjugate base] c) An effective buffer has a [base]/[acid] ratio in the range of 10 - 100. d) An effective buffer has very small absolute concentrations of acid and conjugate base. e) None of the above are true.

b) A buffer is most resistant to pH change when [acid] = [conjugate base]

Define buffer capacity. a) Buffer capacity is the amount of acid that can be added until all of the base is used up. b) Buffer capacity is the amount of acid or base that can be added to a buffer without destroying its effectiveness. c) Buffer capacity is the amount of base that can be added until all of the base is used up. d) Buffer capacity is the amount of base that can be added until all of the acid is used up. e) Buffer capacity is the amount of acid that can be added until all of the acid is used up.

b) Buffer capacity is the amount of acid or base that can be added to a buffer without destroying its effectiveness.

Identify a good buffer. a) significant amounts of both a weak acid and a strong acid b) significant amounts of both a weak acid and its conjugate base c) small amounts of both a strong acid and a strong base d) significant amounts of both a strong acid and a strong base e) small amounts of both a weak acid and its conjugate base

b) significant amounts of both a weak acid and its conjugate base

When titrating a monoprotic strong acid with a weak base at 25°C, the a) pH will be 7 at the equivalence point. b) pH will be greater than 7 at the equivalence point. c) pH will be less than 7 at the d) equivalence point. titration will require more moles of acid than base to reach the equivalence point. e) titration will require more moles of the base than acid to reach the equivalence point.

c) pH will be less than 7 at the

Which one of the following statements is TRUE? a) A buffer can absorb an unlimited amount of base. b) A buffer is an aqueous solution composed of two weak acids. c) A buffer does not change pH when strong acid is added. d) A buffer resists pH change by neutralizing added acids and bases. e) None of the above are true.

d) A buffer resists pH change by neutralizing added acids and bases.

Which of the following solutions is a good buffer system? a) A solution that is 0.10 M LiOH and 0.10 M HNO₃ b) A solution that is 0.10 M HCN and 0.10 M Na I c) A solution that is 0.10 M NaCl and 0.10 M HCl d) A solution that is 0.10 M HCN and 0.10 M LiCN e) A solution that is 0.10 M HNO₃ and 0.10 M LiNO₃

d) A solution that is 0.10 M HCN and 0.10 M LiCN

If the pKa of HCHO2 is 3.74 and the pH of an HCHO2/NaCHO2 solution is 3.11, which of the following is TRUE? a) [HCHO₂] < [NaCHO₂] b) [HCHO₂] = [NaCHO₂] c) [HCHO₂] << [NaCHO₂] d) [HCHO₂] > [NaCHO₂] e) It is not possible to make a buffer of this pH from HCHO₂ and NaCHO₂.

d) [HCHO₂] > [NaCHO₂]

When titrating a weak monoprotic acid with NaOH at 25°C, the a) titration will require more moles of base than acid to reach the equivalence point. b) pH will be equal to 7 at the equivalence point. c) titration will require more moles of acid than base to reach the equivalence point. d) pH will be less than 7 at the equivalence point. e) pH will be greater than 7 at the equivalence point.

e) pH will be greater than 7 at the equivalence point.