Chapter 18: The Representative Elements

Write balanced equations describing the reaction of lithium metal with each of the following: ${\mathit{o}}_{\mathbf{2}}$, ${\mathit{s}}_{\mathbf{8}}$, $\mathit{C}{\mathit{l}}_{\mathbf{2}}$, ${\mathit{P}}_{\mathbf{4}}$,${\mathit{H}}_{\mathbf{2}}$, ${\mathit{H}}_{\mathbf{2}}\mathit{O}$ and Hcl.

What is the molecular structure for each of the following molecules or ions?

a. ${\text{OCl}}_{\text{2}}$

b.${\text{ClO}}_{\text{4}}^{\text{-}}$${\text{ClO}}_{\text{4}}^{\text{-}}$

c.${\text{ICl}}_{\text{5}}$

d.${\text{PF}}_{\text{6}}^{\text{-}}$

Indium(III) phosphide is a semiconducting material that has been frequently used in lasers, light-emitting diodes (LED), and fiberoptic devices. This material can be synthesized at 900. K according to the following reaction:

$In\left(CH3\right)3\left(g\right)+1PH3\left(g\right)\to 88nInP\left(s\right)+13CH4\left(g\right)$

a. If 2.56 L In(CH3)3 at 2.00 atm is allowed to react with 1.38 L PH3 at 3.00 atm, what mass of InP(s) will be produced assuming the reaction is 87% efficient?

b. When an electric current is passed through an optoelectronic device containing InP, the light emitted has an energy of 2.03 3 10219 J. What is the wavelength of this light, and is it visible to the human eye?

c. The semiconducting properties of InP can be altered by doping. If a small number of phosphorus atoms are replaced by atoms with an electron configuration of [Kr]5s24d105p4, is this n-type or p-type doping?

While selenic acid has the formula ${\mathbf{\text{H}}}_{\mathbf{\text{2}}}{\mathbf{\text{SeO}}}_{\mathbf{\text{4}}}$and thus is directly related to sulfuric acid, telluric acid is best visualized as ${\mathbf{\text{H}}}_{\mathbf{\text{6}}}{\mathbf{\text{TeO}}}_{\mathbf{\text{6}}}\mathbf{\text{orTe}}{\mathbf{\left(}\mathbf{\text{OH}}\mathbf{\right)}}_{\mathbf{\text{6}}}$.

(a) What is the oxidation state of tellurium in $\mathbf{\text{Te}}{\mathbf{\left(}\mathbf{\text{OH}}\mathbf{\right)}}_{\mathbf{\text{6}}}$?

(b) Despite its structural differences with sulfuric and selenic acid, telluric acid is a diprotic acid with ${\mathbf{\text{pK}}}_{{\mathbf{\text{a}}}_{\mathbf{\text{1}}}}\mathbf{=}{\mathbf{\text{7.68andpK}}}_{{\mathbf{\text{a}}}_{\mathbf{\text{2}}}}\mathbf{=}\mathbf{\text{11.29}}$. Telluric acid can be prepared by hydrolysis of tellurium hexafluoride according to the equation

${\mathbf{\text{TeF}}}_{\mathbf{\text{6}}}\mathbf{\left(}\mathit{g}\mathbf{\right)}\mathbf{+}{\mathbf{\text{6H}}}_{\mathbf{\text{2}}}\mathbf{\text{O}}\mathbf{\left(}\mathit{l}\mathbf{\right)}\mathbf{\to }{\mathbf{\text{Te(OH)}}}_{\mathbf{\text{6}}}\mathbf{\left(}\mathit{a}\mathit{q}\mathbf{\right)}\mathbf{+}\mathbf{\text{6HF}}\mathbf{\left(}\mathit{a}\mathit{q}\mathbf{\right)}$

Tellurium hexafluoride can be prepared by the reaction of elemental tellurium with fluorine gas:

$\mathbf{\text{Te}}\mathbf{\left(}\mathit{s}\mathbf{\right)}\mathbf{+}\mathbf{3}{\mathbf{\text{F}}}_{\mathbf{\text{2}}}\mathbf{\left(}\mathit{g}\mathbf{\right)}\mathbf{\to }{\mathbf{\text{TeF}}}_{\mathbf{\text{6}}}\mathbf{\left(}\mathit{g}\mathbf{\right)}$

If a cubic block of tellurium (density localid="1663782855001" $\mathbf{=}\mathbf{6}\mathbf{.}\mathbf{240}\raisebox{1ex}{$\mathbf{\text{g}}$}\!\left/ \!\raisebox{-1ex}{${\mathbf{\text{cm}}}^{\mathbf{\text{3}}}$}\right.$) measuring $\mathbf{\text{0.545cm}}$on edge is allowed to react with $\mathbf{\text{2.34L}}$fluorine gas at $\mathbf{\text{1.06atm}}$and $\mathbf{\text{25°C}}$, what is the $\mathbf{\text{pH}}$of a solution of $\mathbf{\text{Te}}{\mathbf{\left(}\mathbf{\text{OH}}\mathbf{\right)}}_{\mathbf{\text{6}}}$formed by dissolving the isolated ${\mathbf{\text{TeF}}}_{\mathbf{\text{6}}}\mathbf{\left(}\mathbf{g}\mathbf{\right)}$in $\mathbf{\text{115mL}}$solution? Assume $\mathbf{\text{100\%}}$ yield in all reactions.

Sodium tripolyphosphate $\mathbf{\left(}{\mathbf{\text{Na}}}_{\mathbf{\text{5}}}{\mathbf{\text{P}}}_{\mathbf{\text{3}}}{\mathbf{\text{O}}}_{\mathbf{\text{10}}}\mathbf{\right)}$is used in many synthetic detergents. Its major effect is to soften the water by complexing role="math" localid="1663829263651" ${\mathbf{\text{Mg}}}^{\mathbf{\text{2+}}}{\mathbf{\text{andCa}}}^{\mathbf{\text{2+}}}$ions. It also increases the efficiency of surfactants, or wetting agents that lower a liquid’s surface tension. The pK value for the formation of ${\mathbf{\text{MgP}}}_{\mathbf{\text{3}}}{{\mathbf{\text{O}}}_{\mathbf{\text{10}}}}^{\mathbf{\text{3-}}}$is role="math" localid="1663830233340" $\mathbf{\text{-8.60}}$. The reaction is ${\mathbf{\text{Mg}}}^{\mathbf{\text{2+}}}\mathbf{+}{\mathbf{\text{P}}}_{\mathbf{\text{3}}}{{\mathbf{\text{O}}}_{\mathbf{\text{10}}}}^{\mathbf{\text{5-}}}\mathbf{\rightleftarrows }{\mathbf{\text{MgP}}}_{\mathbf{\text{3}}}{{\mathbf{\text{O}}}_{\mathbf{\text{10}}}}^{\mathbf{\text{3-}}}$. Calculate the concentration of ${\mathbf{\text{Mg}}}^{\mathbf{\text{2+}}}$in a solution that was originally $\mathbf{50}$. $\mathbf{\text{ppm}}$($\mathbf{\text{50.mg}}\mathbf{/}\mathbf{\text{L}}$of solution) after $\mathbf{\text{40.g}}$of ${\mathbf{\text{Na}}}_{\mathbf{\text{5}}}{\mathbf{\text{P}}}_{\mathbf{\text{3}}}{\mathbf{\text{O}}}_{\mathbf{\text{10}}}$is added to $\mathbf{\text{1.0L}}$ of the solution.

Nitrogen gas reacts with hydrogen gas to form ammonia gas $\mathbf{\left(}{\mathbf{\text{NH}}}_{\mathbf{\text{3}}}\mathbf{\right)}$. Consider the following illustration representing the original reaction mixture (the numbers of each molecule shown are relative numbers):

Assume this reaction mixture goes to completion. The piston apparatus allows the container volume to change in order to keep the pressure constant at $\mathbf{\text{1.00atm}}$. Assume ideal behaviour and constant temperature.

(a) What is the partial pressure of ammonia in the container when the reaction is complete?

(b) What is the mole fraction of ammonia in the container when the reaction is complete?

(c) What is the volume of the container when the reaction is complete?

Using data from Appendix $\mathbf{4}$, calculate ${\mathbf{\text{ΔH}}}^{\mathbf{\text{o}}}{\mathbf{\text{,ΔG}}}^{\mathbf{\text{o}}}$, and${\mathbf{\text{K}}}_{\mathbf{\text{p}}}$ (at $\mathbf{\text{298K}}$) for the production of ozone from oxygen:

role="math" localid="1663835974541" ${\mathbf{\text{3O}}}_{\mathbf{\text{2}}}\mathbf{\left(}\mathbf{g}\mathbf{\right)}\mathbf{\rightleftharpoons }{\mathbf{\text{2O}}}_{\mathbf{\text{3}}}\mathbf{\left(}\mathbf{g}\mathbf{\right)}$

At$\mathbf{\text{30km}}$ above the surface of the earth, the temperature is about$\mathbf{\text{230K}}$ and the partial pressure of oxygen is about $\mathbf{\text{1.0}}\mathbf{\times }{\mathbf{\text{10}}}^{\mathbf{-}\mathbf{3}}\mathbf{\text{atm}}$. Estimate the partial pressure of ozone in equilibrium with oxygen at$\mathbf{\text{30km}}$ above the earth’s surface. Is it reasonable to assume that the equilibrium between oxygen and ozone is maintained under these conditions? Explain.

You travel to a distant, cold planet where the ammonia flows like water. In fact, the inhabitants of this planet use ammonia (an abundant liquid on their planet) much as earthlings use water. Ammonia is also similar to water in that it is amphoteric and undergoes autoionization. The $\mathbf{\text{K}}$ value for the autoionization of ammonia is$\mathbf{1}\mathbf{.8}\mathbf{\times }{\mathbf{10}}^{\mathbf{-}\mathbf{12}}$ at the standard temperature of the planet. What is the$\mathbf{\text{pH}}$ of ammonia at this temperature?

A proposed two-step mechanism for the destruction of ozone in the upper atmosphere is

(a) What is the overall balanced equation for the ozone destruction reaction?

(b) Which species is a catalyst?

(c) Which species is an intermediate?

(d) What is the rate law derived from this mechanism if the first step in the mechanism is slow and the second step is fast?

(e) One of the concerns about the use of Freons is that they will migrate to the upper atmosphere, where chlorine atoms can be generated by the reaction

$\underset{\mathbf{\text{Feron-12}}}{{\mathbf{\text{CCl}}}_{\mathbf{\text{2}}}{\mathbf{\text{F}}}_{\mathbf{\text{2}}}}\stackrel{\mathbf{\text{hv}}}{\mathbf{\to }}{\mathbf{\text{CF}}}_{\mathbf{\text{2}}}\mathbf{\text{Cl}}\mathbf{+}\mathbf{\text{Cl}}$

Chlorine atoms also can act as a catalyst for the destruction of ozone. The first step of a proposed mechanism for chlorine-catalysed ozone destruction is

$\mathbf{\text{Cl}}\mathbf{\left(}\mathbf{g}\mathbf{\right)}\mathbf{+}{\mathbf{\text{O}}}_{\mathbf{\text{3}}}\mathbf{\left(}\mathbf{g}\mathbf{\right)}\mathbf{\to }\mathbf{\text{ClO}}\mathbf{\left(}\mathbf{g}\mathbf{\right)}\mathbf{+}{\mathbf{\text{O}}}_{\mathbf{\text{2}}}\mathbf{\left(}\mathbf{g}\mathbf{\right)}\mathbf{\text{Slow}}$

Assuming a two-step mechanism, propose the second step in the mechanism and give the overall balanced equation.

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