Chapter 14

Cr atoms can have a wide range of oxidation numbers. Assign oxidation numbers for the Cr atom in each compound, all of which are known compounds. a) \(\mathrm{Na}_{2} \mathrm{Cr} \mathrm{O}_{4}\) b) \(\mathrm{Na}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\) c) \(\mathrm{CrF}_{5}\) d) \(\mathrm{CrCl}_{3}\) e) \(\mathrm{CrCl}_{2}\)

What are two different definitions of oxidation?

Balance this redox reaction by inspection. $$ \mathrm{S}_{8}+\mathrm{O}_{2} \rightarrow \mathrm{SO}_{2} $$

Balance these redox reactions by the half reaction method. a) \(\mathrm{Na}+\mathrm{Hg}_{2} \mathrm{Cl}_{2} \rightarrow \mathrm{NaCl}+\mathrm{Hg}\) b) \(\mathrm{Al}_{2} \mathrm{O}_{3}+\mathrm{C} \rightarrow \mathrm{Al}+\mathrm{CO}_{2}\)

Balance this redox reaction by inspection. $$ \mathrm{C}_{18} \mathrm{H}_{38}+\mathrm{O}_{2} \rightarrow \mathrm{CO}_{2}+\mathrm{H}_{2} \mathrm{O} $$

Balance these redox reactions by the half reaction method. a) \(\mathrm{Br}^{-}+\mathrm{I}_{2} \rightarrow \mathrm{I}^{-}+\mathrm{Br}_{2}\) b) \(\mathrm{CrCl}_{3}+\mathrm{F}_{2} \rightarrow \mathrm{CrF}_{3}+\mathrm{Cl}_{2}\)

Balance this redox reaction by the half reaction method by assuming an acidic solution. $$ \mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}+\mathrm{Fe} \rightarrow \mathrm{Cr}^{3+}+\mathrm{Fe}^{3+} $$

Assign oxidation numbers to the atoms in each substance. a) \(\mathrm{P}_{4}\) b) \(\mathrm{SO}_{3}\) c) \(\mathrm{SO}_{3}^{2-}\) d) \(\mathrm{Ca}_{3}\left(\mathrm{PO}_{3}\right) 2\)

Balance these redox reactions that occur in aqueous solution. Use whatever water-derived species is necessary; there may be more than one correct balanced equation. a) \(\mathrm{Cu}+\mathrm{NO}_{3}^{-} \rightarrow \mathrm{Cu}^{2+}+\mathrm{NO}_{2}\) b) \(\mathrm{Fe}+\mathrm{MnO}_{4}^{-} \rightarrow \mathrm{Fe}^{3+}+\mathrm{Mn}\)

Assign oxidation numbers to the atoms in each substance. a) \(\mathrm{PCl}_{5}\) b) \(\left(\mathrm{NH}_{4}\right)_{2} \mathrm{Se}\) c) Ag d) \(\mathrm{Li}_{2} \mathrm{O}_{2}\)