Chapter 22

Dinitrogen pentoxide is a product of the reaction between \(\mathrm{P}_{4} \mathrm{O}_{10}\) and \(\mathrm{HNO}_{3}\). Write a balanced equation for this reaction. Calculate the theoretical yield of \(\mathrm{N}_{2} \mathrm{O}_{5}\) if \(79.4 \mathrm{~g}\) of \(\mathrm{P}_{4} \mathrm{O}_{10}\) are reacted with an excess of \(\mathrm{HNO}_{3}\). (Hint: One of the products is \(\mathrm{HPO}_{3}\).)

Explain why (a) \(\mathrm{NH}_{3}\) is more basic than \(\mathrm{PH}_{3}\) (b) \(\mathrm{NH}_{3}\) has a higher boiling point than \(\mathrm{PH}_{3}\), (c) \(\mathrm{PCl}_{5}\) exists but \(\mathrm{NCl}_{5}\) does not, \((\mathrm{d}) \mathrm{N}_{2}\) is more inert than \(\mathrm{P}_{4}\).

What is the hybridization of phosphorus in the phosphonium ion, \(\mathrm{PH}_{4}^{+} ?\).

Describe one industrial and one laboratory preparation of \(\mathrm{O}_{2}\).

Give an account of the various kinds of oxides that exist and illustrate each type by two examples.

Hydrogen peroxide can be prepared by treating barium peroxide with sulfuric acid. Write a balanced equation for this reaction.

Describe the Frasch process for obtaining sulfur.

Describe the contact process for the production of sulfuric acid.

How is hydrogen sulfide generated in the laboratory?

Draw molecular orbital energy level diagrams for \(\mathrm{O}_{2}, \mathrm{O}_{2}^{-},\) and \(\mathrm{O}_{2}^{2-}\).

Hydrogen peroxide is unstable and decomposes readily: $$2 \mathrm{H}_{2} \mathrm{O}_{2}(a q) \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}(l)+\mathrm{O}_{2}(g)$$ This reaction is accelerated by light, heat, or a catalyst. (a) Explain why hydrogen peroxide sold in drugstores comes in dark bottles. (b) The concentrations of aqueous hydrogen peroxide solutions are normally expressed as percent by mass. In the decomposition of hydrogen peroxide, how many liters of oxygen gas can be produced at STP from \(15.0 \mathrm{~g}\) of a 7.50 percent hydrogen peroxide solution?

What are the oxidation numbers of \(\mathrm{O}\) and \(\mathrm{F}\) in \(\mathrm{HFO} ?\)

Oxygen forms double bonds in \(\mathrm{O}_{2}\), but sulfur forms single bonds in \(\mathrm{S}_{8}\). Explain.

Sulfuric acid is a dehydrating agent. Write balanced equations for the reactions between sulfuric acid and the following substances: (a) \(\mathrm{HCOOH}\) (b) \(\mathrm{H}_{3} \mathrm{PO}_{4}\) (c) \(\mathrm{HNO}_{3}\), (d) \(\mathrm{HClO}_{3}\). (Hint: Sulfuric acid is not decomposed by the dehydrating action.)

\(\mathrm{SF}_{6}\) exists but \(\mathrm{OF}_{6}\) does not. Explain.

Explain why \(\mathrm{SCl}_{6}, \mathrm{SBr}_{6},\) and \(\mathrm{SI}_{6}\) cannot be prepared.

Compare the physical and chemical properties of \(\mathrm{H}_{2} \mathrm{O}\) and \(\mathrm{H}_{2} \mathrm{~S}\).

The bad smell of water containing hydrogen sulfide can be removed by the action of chlorine. The reaction is $$\mathrm{H}_{2} \mathrm{~S}(a q)+\mathrm{Cl}_{2}(a q) \longrightarrow 2 \mathrm{HCl}(a q)+\mathrm{S}(s)$$ If the hydrogen sulfide content of contaminated water is 22 ppm by mass, calculate the amount of \(\mathrm{Cl}_{2}\) (in grams) required to remove all the \(\mathrm{H}_{2} \mathrm{~S}\) from \(2.0 \times 10^{2}\) gallons of water. ( 1 gallon \(=3.785\) L.)

Describe two reactions in which sulfuric acid acts as an oxidizing agent.

Concentrated sulfuric acid reacts with sodium iodide to produce molecular iodine, hydrogen sulfide, and sodium hydrogen sulfate. Write a balanced equation for the reaction.

Describe an industrial method for preparing each of the halogens.

Name the major uses of the halogens.

Metal chlorides can be prepared in a number of ways: (a) direct combination of metal and molecular chlorine, (b) reaction between metal and hydrochloric acid, (c) acid-base neutralization, (d) metal carbonate treated with hydrochloric acid, (e) precipitation reaction. Give an example for each type of preparation.

Sulfuric acid is a weaker acid than hydrochloric acid. Yet hydrogen chloride is evolved when concentrated sulfuric acid is added to sodium chloride. Explain.

Show that chlorine, bromine, and iodine are very much alike by giving an account of their behavior (a) with hydrogen, (b) in producing silver salts, (c) as oxidizing agents, and (d) with sodium hydroxide. (e) In what respects is fluorine not a typical halogen element?

Draw structures for (a) (HF) \(_{2}\), (b) \(\mathrm{HF}_{2}^{-}\).

Hydrogen fluoride can be prepared by the action of sulfuric acid on sodium fluoride. Explain why hydrogen bromide cannot be prepared by the action of the same acid on sodium bromide.

Aqueous copper(II) sulfate solution is blue. When aqueous potassium fluoride is added to the \(\mathrm{CuSO}_{4}\) solution, a green precipitate is formed. If aqueous potassium chloride is added instead, a bright-green solution is formed. Explain what happens in each case.

Use the VSEPR method to predict the geometries of the following species: (a) \(\mathrm{I}_{3}^{-},\) (b) \(\mathrm{SiCl}_{4},\) (c) \(\mathrm{PF}_{5}\), (d) \(\mathrm{SF}_{4}\).

Iodine pentoxide, \(\mathrm{I}_{2} \mathrm{O}_{5}\), is sometimes used to remove carbon monoxide from the air by forming carbon dioxide and iodine. Write a balanced equation for this reaction and identify species that are oxidized and reduced.

Write a balanced equation for each of the following reactions: (a) Heating phosphorous acid yields phosphoric acid and phosphine \(\left(\mathrm{PH}_{3}\right) .\) (b) Lithium carbide reacts with hydrochloric acid to give lithium chloride and methane. (c) Bubbling HI gas through an aqueous solution of \(\mathrm{HNO}_{2}\) yields molecular iodine and nitric oxide. (d) Hydrogen sulfide is oxidized by chlorine to give \(\mathrm{HCl}\) and \(\mathrm{SCl}_{2}\).

(a) Which of the following compounds has the greatest ionic character: \(\mathrm{PCl}_{5}, \mathrm{SiCl}_{4}, \mathrm{CCl}_{4}, \mathrm{BCl}_{3} ?\) (b) Which of the following ions has the smallest ionic radius: \(\mathrm{F}^{-}, \mathrm{C}^{4-}, \mathrm{N}^{3-}, \mathrm{O}^{2-} ?(\mathrm{c})\) Which of the following atoms has the highest ionization energy: \(\mathrm{F}, \mathrm{Cl}, \mathrm{Br}, \mathrm{I} ?(\mathrm{~d})\) Which of the following oxides is most acidic: \(\mathrm{H}_{2} \mathrm{O}, \mathrm{SiO}_{2}, \mathrm{CO}_{2} ?\)

Both \(\mathrm{N}_{2} \mathrm{O}\) and \(\mathrm{O}_{2}\) support combustion. Suggest one physical and one chemical test to distinguish between the two gases.

What is the change in oxidation number for the following reaction? $$3 \mathrm{O}_{2} \longrightarrow 2 \mathrm{O}_{3}$$

Describe the bonding in the \(\mathrm{C}_{2}^{2-}\) ion in terms of the molecular orbital theory.

Starting with deuterium oxide \(\left(\mathrm{D}_{2} \mathrm{O}\right),\) describe how you would prepare (a) \(\mathrm{NaOD}\) (b) DCl, (c) \(\mathrm{ND}_{3}\) (d) \(\mathrm{C}_{2} \mathrm{D}_{2}\) (e) \(\mathrm{CD}_{4}\), (f) \(\mathrm{D}_{2} \mathrm{SO}_{4}\).

Solid \(\mathrm{PCl}_{5}\) exists as \(\left[\mathrm{PCl}_{4}^{+}\right]\left[\mathrm{PCl}_{6}^{-}\right] .\) Draw Lewis structures for these ions. Describe the hybridization state of the \(\mathrm{P}\) atoms.

Consider the Frasch process. (a) How is it possible to heat water well above \(100^{\circ} \mathrm{C}\) without turning it into steam? (b) Why is water sent down the outermost pipe? (c) Why would excavating a mine and digging for sulfur be a dangerous procedure for obtaining the element?

Predict the physical and chemical properties of astatine, a radioactive element and the last member of Group 7A.

Lubricants used in watches usually consist of longchain hydrocarbons. Oxidation by air forms solid polymers that eventually destroy the effectiveness of the lubricants. It is believed that one of the initial steps in the oxidation is removal of a hydrogen atom (hydrogen abstraction). By replacing the hydrogen atoms at reactive sites with deuterium atoms, it is possible to substantially slow the overall oxidation rate. Why? (Hint: Consider the kinetic isotope effect.)

How are lightbulbs frosted? (Hint: Consider the action of hydrofluoric acid on glass, which is made of silicon dioxide.

Life evolves to adapt to its environment. In this respect, explain why life most frequently needs oxygen for survival, rather than the more abundant nitrogen.

As mentioned in Chapter 3 , ammonium nitrate is the most important nitrogen- containing fertilizer in the world. Given only air and water as starting materials and any equipment and catalyst at your disposal, describe how you would prepare ammonium nitrate. State conditions under which you can increase the yield in each step.