Write and balance reactions for the following situations:
a. The burning of titanium metal in oxygen gas to produce titanium(IV) dioxide, TiO2.
b. The "burning" of titanium metal in a pure nitrogen gas atmosphere to produce titanium(III) nitride, TiN.
c. The production of sulfuric acid by reacting sulfur, oxygen, and water.
d. Production of antimony metal from the reaction of antimony oxide and hydrogen gas. Water is also product of this reaction.