Molybdenum is obtained as a by-product of copper mining or is mined directly (primary deposits are in the Rocky Mountains in Colorado). In both cases it is obtained as MoS2, which is then converted to MoO3. The MoO3 can be used directly in the production of stainless steel for high-speed tools (which accounts for about 85% of the molybdenum used). Molybdenum can be purified by dis-solving MoO3 in aqueous ammonia and crystallizing am-monium molybdate. Depending on conditions, either (NH4)2Mo2O7 or (NH4)6Mo7O24 • 4H2O is obtained.
a. Give names for MoS2 and MoO3.
b. What is the oxidation state of Mo in each of the com-pounds mentioned above?