5. (6 marks) Arsenic acid, H3AsO4, is a triprotic weak acid with the following Ka.
pKa1 = 2.26 pKa2 = 6.76
pKa3 = 11.26 to convert: Ka = 10^(-pKa)
a) (3 marks) Is a solution of NaH2AsO4 acidic, basic, or neutral? Write two equilibrium equations that illustrate that an aqueous solution of NaH2AsO4 can act either as an acid or a base in pure water. Show quantitatively which of the two equilibria dominates.
b) (3 marks) Is a solution of Na2HAsO4 acidic, basic, or neutral? Write two equilibrium equations that illustrate that an aqueous solution of Na2HAsO4 can act either as an acid or a base in pure water. Show quantitatively which of the two equilibria dominates.