Identify each of the following unbalanced reaction equations as belonging to one or more of the following categories: precipitation, acid-base, or oxidation-reduction.
a. $\mathrm{Fe}(s)+\mathrm{H}_{2} \mathrm{SO}_{4}(a q) \rightarrow \mathrm{Fe}_{3}\left(\mathrm{SO}_{4}\right)_{2}(a q)+\mathrm{H}_{2}(g)$
b. $\mathrm{HClO}_{4}(a q)+\mathrm{RbOH}(a q) \rightarrow \mathrm{RbClO}_{4}(a q)+\mathrm{H}_{2} \mathrm{O}(l)$
c. $\mathrm{Ca}(s)+\mathrm{O}_{2}(g) \rightarrow \mathrm{CaO}(s)$
d. $\mathrm{H}_{2} \mathrm{SO}_{4}(a q)+\mathrm{NaOH}(a q) \rightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}(a q)+\mathrm{H}_{2} \mathrm{O}(l)$
e. $\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}(a q)+\mathrm{Na}_{2} \mathrm{CO}_{3}(a q) \rightarrow \mathrm{PbCO}_{3}(s)+\mathrm{NaNO}_{3}(a q)$
f. $\mathrm{K}_{2} \mathrm{SO}_{4}(a q)+\mathrm{CaCl}_{2}(a q) \rightarrow \mathrm{KCl}(a q)+\mathrm{CaSO}_{4}(s)$
g. $\mathrm{HNO}_{3}(a q)+\mathrm{KOH}(a q) \rightarrow \mathrm{KNO}_{3}(a q)+\mathrm{H}_{2} \mathrm{O}(l)$
h. $\mathrm{Ni}\left(\mathrm{C}_{2} \mathrm{H}_{3} \mathrm{O}_{2}\right)_{2}(a q)+\mathrm{Na}_{2} \mathrm{~S}(a q) \rightarrow \mathrm{NiS}(s)+\mathrm{NaC}_{2} \mathrm{H}_{3} \mathrm{O}_{2}(a q)$
i. $\mathrm{Ni}(s)+\mathrm{Cl}_{2}(g) \rightarrow \mathrm{NiCl}_{2}(s)$