Chapter 19

Identify each of the following changes as either oxidation or reduction. a. $2{Cl}^{-}\to {Cl}_2+2e^{-}$ c. ${Ca}^{-2}+2e^{-}\to 2Ca$ b. $Na\to {Na}^{+}+e^{-}$ {d} . $O_2+4{\mathrm{e}}^{-}\to 2O^{2-}$

Identify the reducing agents in these equations a. $4{\mathrm{NH}}_3+5{\mathrm{O}}_2\to 4\mathrm{NO}+6{\mathrm{H}}_2\mathrm{O}$ b. ${\mathrm{Na}}_2{\mathrm{SO}}_4+4\mathrm{C}\to {\mathrm{Na}}_2\mathrm{S}+4\mathrm{CO}$ c. $4{\mathrm{IrF}}_5+\mathrm{Ir}\to 5\mathrm{Ir}\mathrm{F}4$

Write a balanced ionic redox equation using the following pairs of redox half- reactions. a. $\mathrm{Fe}\to {\mathrm{Fe}}^{2+}+2{\mathrm{e}}^{-}$ ${\mathrm{Te}}^{2+}+2{\mathrm{e}}^{-}\to \mathrm{Te}$ b. IO ${}_4^{-}+2{\mathrm{e}}^{-}\to {\mathrm{IO}}_3^{-}$ Al $\to {\mathrm{Al}}^{3+}+3{\mathrm{e}}^{-}$ (in acid solution) $c.I_2+2{\mathrm{e}}^{-}\to 2{\mathrm{I}}^{-}$ ${\mathrm{N}}_2\mathrm{O}\to {\mathrm{NO}}_3^{-}+4{\mathrm{e}}^{-}(\text{ in acid solution })$

Balance these ionic redox equations by any method. a. ${\mathrm{Sb}}^{3+}+{\mathrm{MnO}}_4^{-}\to {\mathrm{SbO}}_4^{3-}+{\mathrm{Mn}}^{2+}(\text{ in acid solution })$ b. ${\mathrm{N}}_2\mathrm{O}+{\mathrm{ClO}}^{-}\to {\mathrm{Cl}}^{-}+{\mathrm{NO}}_2^{-}$ (in basic solution)

Gemstones Rubies are gemstones made up mainly of aluminum oxide. Their red color comes from a small amount of chromium(III) ions replacing some of the aluminum ions. Draw the structure of aluminum oxide, and show the reaction in which an aluminum ion is replaced with a chromium ion. Is this a redox reaction?

Balance these ionic redox equations by any method. a. $\mathrm{Mg}+{\mathrm{Fe}}^{3+}\to {\mathrm{Mg}}^{2+}+\mathrm{Fe}$ b. ${\mathrm{ClO}}_3^{-}+{\mathrm{SO}}_2\to {\mathrm{Cl}}^{-}+{\mathrm{SO}}_4^{2-}(\text{ in acid solution })$

Balance these redox equations by any method. a. $P+H_{2}O+HN{O}_3\to H_{3}P{O}_4+NO$ b. $KCl{O}_3+HCl\to C{l}_2+Cl{O}_2+H_{2}O+KCl$

Apply The following equations show redox reactions that are sometimes used in the laboratory to generate pure nitrogen gas and pure dinitrogen monoxide gas (nitrous oxide, ${\mathrm{N}}_2\mathrm{O})$ $${\mathrm{NH}}_4{\mathrm{NO}}_2(\mathrm{s})\to {\mathrm{N}}_2(\mathrm{g})+2{\mathrm{H}}_2\mathrm{O}(\mathrm{l})$$ $${\mathrm{NH}}_4{\mathrm{NO}}_3(\mathrm{s})\to {\mathrm{N}}_2\mathrm{O}(\mathrm{g})+2{\mathrm{H}}_2\mathrm{O}(\mathrm{l})$$ a. Determine the oxidation number of each element in the two equations, and then make diagrams showing the changes in oxidation numbers that occur in each reaction. b. Identify the atom that is oxidized and the atom that is reduced in each of the two reactions. c. Identify the oxidizing and reducing agents in each of the two reactions. d. Write a sentence telling how the electron transfer taking place in these two reactions differs from that taking place here $$2{\mathrm{AgNO}}_3+\mathrm{Zn}\to \mathrm{Zn}{\left({\mathrm{NO}}_3\right)}_2+2\mathrm{Ag}$$

Predict Consider the fact that all of the following are stable compounds. What can you infer about the oxidation state of phosphorus in its compounds? $${\mathrm{PH}}_3,{\mathrm{PCI}}_3,{\mathrm{P}}_2{\mathrm{H}}_4,{\mathrm{PCI}}_5,{\mathrm{H}}_3{\mathrm{PO}}_4,{\mathrm{Na}}_3{\mathrm{PO}}_3$$

Solve Potassium permanganate oxidizes chloride ions to chlorine gas. Balance the equation for this redox reaction taking place in acid solution