SAT Subject Test Chemistry
PART 2
REVIEW OF MAJOR TOPICS
CHAPTER 11
Acids, Bases, and Salts
AMPHOTERIC SUBSTANCES
Some substances, such as the HCO3− ion, the HSO4− ion, the H2O molecule, and the NH3 molecule, can act as either proton donors (acids) or proton receivers (bases), depending upon which other substances they come into contact with. These substances are said to be amphoteric. Amphoteric substances donate protons in the presence of strong bases and accept protons in the presence of strong acids.
Examples are the reactions of the bisulfate ion, HSO4−:
With a strong acid, HSO4− accepts a proton:
HSO4−(aq)+H+(aq) → H2SO4(aq)
With a strong acid, HSO4− donates a proton:
HSO4−(aq)+OH−(aq) → H2O()+SO42−(aq)