Chapter 18: The Representative Elements

Write a balanced equation describing the reduction of ${\mathbf{\text{H}}}_{\mathbf{\text{2}}}{\mathbf{\text{SeO}}}_{\mathbf{\text{4}}}$by${\mathbf{\text{SO}}}_{\mathbf{\text{2}}}$ to produce selenium.

What is the valence electron configuration of the halogens? Why do the boiling points and melting points of the halogens increase steadily from${\mathbf{\text{F}}}_{\mathbf{\text{2}}}$to${\mathbf{\text{I}}}_{\mathbf{\text{2}}}$?

Draw the Lewis structure of ${\mathbf{\text{O}}}_{\mathbf{\text{2}}}{\mathbf{\text{F}}}_{\mathbf{\text{2}}}$ . Assign oxidation states and formal charges to the atoms in${\mathbf{\text{O}}}_{\mathbf{\text{2}}}{\mathbf{\text{F}}}_{\mathbf{\text{2}}}$ . The compound${\mathbf{\text{O}}}_{\mathbf{\text{2}}}{\mathbf{\text{F}}}_{\mathbf{\text{2}}}$ is a vigorous and potent oxidizing and fluorinating agent. Are oxidation states or formal charges more useful in accounting for these properties of${\mathbf{\text{O}}}_{\mathbf{\text{2}}}{\mathbf{\text{F}}}_{\mathbf{\text{2}}}$ ?

The oxidation states of the halogens vary from -1to +7. Identify compounds of chlorine that have$\mathbf{-}\mathbf{1}\mathbf{,}\mathbf{+}\mathbf{1}\mathbf{,}\mathbf{+}\mathbf{3}\mathbf{,}\mathbf{+}\mathbf{5}$ and$\mathbf{+}\mathbf{7}$oxidation states. How does the oxyacid strength of the halogens vary as the number of oxygens in the formula increases?

Give two reasons why ${\mathbf{F}}_{\mathbf{2}}$ is the most reactive of the halogens.

What is the valence electron configuration for the alkali metals? List some common properties of alkali metals. How are the pure metals prepared?

Explain why HFis a weak acid, whereas$\mathbf{HCl}\mathbf{,}\mathbf{}\mathbf{HBr}$, and HIare all strong acids.

Hydrazine is somewhat toxic. Use the following half-reactions to explain why household bleach (highly alkaline solutions of sodium hypochlorite) should not be mixed with household ammonia or glass cleansers that contain ammonia.

${\mathbf{ClO}}^{\mathbf{-}}\mathbf{+}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}\mathbf{+}\mathbf{2}{\mathbf{e}}^{\mathbf{-}}\mathbf{\to }\mathbf{2}{\mathbf{OH}}^{\mathbf{-}}\mathbf{+}{\mathbf{Cl}}^{\mathbf{-}}$ $\mathit{\epsilon }\mathbf{°}\mathbf{=}\mathbf{0}\mathbf{.}\mathbf{90}\mathbf{}\mathbf{V}$

${\mathbf{N}}_{\mathbf{2}}{\mathbf{H}}_{\mathbf{4}}\mathbf{+}\mathbf{2}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}\mathbf{+}\mathbf{2}{\mathbf{e}}^{\mathbf{-}}\mathbf{\to }\mathbf{2}{\mathbf{NH}}_{\mathbf{3}}\mathbf{+}\mathbf{2}{\mathbf{OH}}^{\mathbf{-}}$$\mathit{\epsilon }\mathbf{°}\mathbf{=}\mathbf{-}\mathbf{0}\mathbf{.}\mathbf{10}\mathbf{}\mathbf{V}$

What is a disproportionation reaction? Use the following reduction potentials:

$\mathbf{Cl}{{\mathbf{O}}_{\mathbf{3}}}^{\mathbf{-}}\mathbf{+}\mathbf{3}{\mathbf{H}}^{\mathbf{+}}\mathbf{+}\mathbf{2}{\mathbf{e}}^{\mathbf{-}}\mathbf{\to }{\mathbf{HClO}}_{\mathbf{2}}\mathbf{+}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}$$\mathit{\epsilon }\mathbf{°}\mathbf{=}\mathbf{0}\mathbf{.}\mathbf{90}\mathbf{}\mathbf{V}$

${\mathbf{HClO}}_{\mathbf{2}}\mathbf{+}\mathbf{2}{\mathbf{H}}^{\mathbf{+}}\mathbf{+}\mathbf{2}{\mathbf{e}}^{\mathbf{-}}\mathbf{\to }\mathbf{HClO}\mathbf{+}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}$$\mathit{\epsilon }\mathbf{°}\mathbf{=}\mathbf{1}\mathbf{.}\mathbf{65}\mathbf{}\mathbf{V}$

Photography lenses contain small embedded crystals of solid silver chloride. Silver chloride is light-sensitive because of the reaction:

$\mathbf{AgCl}\mathbf{\left(}\mathbf{s}\mathbf{\right)}\stackrel{\mathbf{h}\mathbf{\nu }}{\mathbf{\to }}\mathbf{Ag}\mathbf{\left(}\mathbf{s}\mathbf{\right)}\mathbf{+}\mathbf{Cl}\mathbf{\left(}\mathbf{s}\mathbf{\right)}$

Small particles of metallic silver cause the lenses to darken. In the lenses, this process is reversible. When the light is removed, the reverse reaction occurs. However, when pure white silver chloride is exposed to sunlight, it darkens; the reverse reaction does not occur in the dark. (a). How do you explain this difference? (b). Photography lenses do become permanently dark in time. How do you account for this?