Chapter 18: The Representative Elements

Trisodium phosphate $\left(\text{TSP}\right)$is an effective grease remover. Like many cleaners,$\mathbf{\text{TSP}}$acts as a base in water. Write a balanced equation to account for this basic behaviour.

White phosphorus is much more reactive than black or red phosphorus. Explain.

Arsenic reacts with oxygen to form oxides analogous to the phosphorus oxides. These arsenic oxides react with water similarly to the phosphorus oxides. Write balanced chemical equations describing the reaction of arsenic with oxygen and the reaction of the oxides with water.

Compare the description of the localized electron model (Lewis structure) with that of the molecular orbital model for the bonding in$\mathbf{\text{NO}}$,${\mathbf{\text{NO}}}^{\mathbf{+}}$, and${\mathbf{\text{NO}}}^{\mathbf{-}}$. Account for any discrepancies between the two models.

Many oxides of nitrogen have positive values for the standard free energy of formation. Using $\mathbf{\text{NO}}$as an example, explain why this is the case.

Label the following hydrides as ionic, covalent, or interstitial, and support your answer. Note: The light blue atoms are hydrogen atoms.

Draw Lewis structures for the ${\mathbf{\text{AsCl}}}_{\mathbf{\text{4}}}^{\mathbf{\text{+}}}$and${\mathbf{\text{AsCl}}}_{\mathbf{\text{6}}}^{\mathbf{\text{-}}}$ions. What type of reaction (acid–base, oxidation–reduction, or the like) is the following?

${\mathbf{\text{2AsCl}}}_{\mathbf{\text{5}}}\mathbf{\text{(g)}}\mathbf{\to }{\mathbf{\text{AsCl}}}_{\mathbf{\text{4}}}{\mathbf{\text{AsCl}}}_{\mathbf{\text{6}}}\mathbf{\text{(s)}}$

In many natural waters, nitrogen and phosphorus are the least abundant nutrients available for plant life. Some waters that become polluted from agricultural runoff or municipal sewage become infested with algae. The algae flourish, and fish life dies off as a result. Describe how these events are chemically related.

Nitric acid is produced commercially by the Ostwald process, represented by the following equations:

$$\begin{gathered} {\mathbf{\text{4NH}}}_{\mathbf{\text{3}}}{\mathbf{\text{(g) + 5O}}}_{\mathbf{\text{2}}}\mathbf{\text{(g)}}\mathbf{\to }{\mathbf{\text{4NO(g) + 6H}}}_{\mathbf{\text{2}}}\mathbf{\text{O(g)}} \\ {\mathbf{\text{2NO(g) +O}}}_{\mathbf{\text{2}}}\mathbf{\text{(g)}}\mathbf{\to }{\mathbf{\text{2NO}}}_{\mathbf{\text{2}}}\mathbf{\text{(g)}} \\ {\mathbf{\text{3NO}}}_{\mathbf{\text{2}}}{\mathbf{\text{(g) +H}}}_{\mathbf{\text{2}}}\mathbf{\text{O(l)}}\mathbf{\to }{\mathbf{\text{2HNO}}}_{\mathbf{\text{3}}}\mathbf{\text{(aq) + NO(g)}} \end{gathered}$$

What mass of${\mathbf{\text{NH}}}_{\mathbf{\text{3}}}$must be used to produce${\mathbf{\text{1.0×10}}}^{\mathbf{\text{6}}}$kg${\mathbf{\text{HNO}}}_{\mathbf{\text{3}}}$by the Ostwald process? Assume$\mathbf{\text{100\%}}$yield in each reaction, and assume that theproduced in the third step is not recycled.

The space shuttle orbiter utilizes the oxidation of methylhydrazine by dinitrogen tetroxide for propulsion:

${\mathbf{\text{4N}}}_{\mathbf{\text{2}}}{\mathbf{\text{H}}}_{\mathbf{\text{3}}}{\mathbf{\text{CH}}}_{\mathbf{\text{3}}}{\mathbf{\text{(l) + 5N}}}_{\mathbf{\text{2}}}{\mathbf{\text{O}}}_{\mathbf{\text{4}}}\mathbf{\text{(l)}}\mathbf{\to }{\mathbf{\text{12H}}}_{\mathbf{\text{2}}}{\mathbf{\text{O(g) + 9N}}}_{\mathbf{\text{2}}}{\mathbf{\text{(g) + 4CO}}}_{\mathbf{\text{2}}}\mathbf{\text{(g)}}$

Calculate$\mathbf{∆}\mathit{H}\mathbf{°}$ for this reaction using data in Appendix $\mathbf{4}$.