The following diagrams contain one or more of the compounds: H2A, NaHA, and Na2A, where H2...

The following diagrams contain one or more of the compounds: H2A, NaHA, and Na2A, where H2A is a weak diprotic acid. (1) Which of the solutions can act as buffer solutions? (2) Which solution is the most effective buffer solution? Water molecules and Na+ ions have been omitted for clarity.