Write skeleton equations for these reactions.
a. iron(s) $+$ fluorine(g) $\rightarrow$ iron (III) fluoride $(s)$
b. sulfur trioxide(g) $+$ water $(1) \rightarrow$ sulfuric acid(aq)
c. sodium(s) + magnesium iodide(aq) $\rightarrow$
sodium iodide(aq) + magnesium(s)
d. vanadium(s) $+$ oxygen $(\mathrm{g}) \rightarrow$ vanadium $(\mathrm{V})$ oxide(s)