A black powder is known to be an oxide with the general formula MO₂, where M is a transition-metal element. When a 2.850 g sample of the oxide is heated in a stream of hydrogen gas, the oxygen is removed as water vapor, leaving 1.710 g of the pure metal.
a. Determine the mass of oxygen that was removed during the reduction.
b. Using the stoichiometry implied by the formula MO₂, calculate the molar mass of the unknown metal M.
c. Identify the element M by comparing the calculated molar mass with values on the periodic table, and cite numerical evidence to support your identification.