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)