19. Which one of the following combinations cannot produce a buffer solution? a) HClO4 and NaClO4 b) HCN and NaCN c) HNO2 and NaNO2 d) NH3 and (NH4)2SO4 e) NH3 and NH4Br 20. Which one of the following combinations is not a buffer solution? a) NH3 and (NH4)2SO4 b) HBr and KBr c) HCN and NaCN d) NH3 and NH4Br e) HC2H3O2 and NaC2H3O2 21. Which of the following statements about buffers is false? a) a buffer resists changes in pH upon addition of small amounts of strong acids and bases b) a buffer solution can react with either H3O+or OH ions c) a buffer solution resists change in pH upon small dilutions d) a buffer always consists of a weak acid and a soluble ionic salt of the weak acid e) most body fluids contain natural buffer systems 22. Choose the response that includes all the following combinations that are buffer solutions and none that are not buffer solutions. All components are present in 0.10M concentrations. I. HCN and NaCN II. NH3 and NH4Cl III. HNO3 and NH4NO3 IV. H2SO4 and NaHSO4 a) I, III, and IV b) I and II c) II, III, and IV d) III and IV e) I and