Chapter 17

Write equilibrium constant expressions for these equilibria. $$ \begin{array}{l}{\text { a. } \mathrm{N}_{2} \mathrm{O}_{4}(\mathrm{g}) \rightleftharpoons 2 \mathrm{NO}_{2}(\mathrm{g})} \\ {\text { b. } 2 \mathrm{H}_{2} \mathrm{S}(\mathrm{g}) \rightleftharpoons 2 \mathrm{H}_{2}(\mathrm{g}) \rightleftharpoons \mathrm{S}_{2}(\mathrm{g})} \\\ {\text { c. } \mathrm{CO}(\mathrm{g})+3 \mathrm{H}_{2}(\mathrm{g}) \rightleftharpoons \mathrm{CH}_{4}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{g})} \\ {\text { d. } 4 \mathrm{NH}_{3}(\mathrm{g})+5 \mathrm{O}_{2}(\mathrm{g}) \rightleftharpoons 4 \mathrm{NO}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{g})} \\ {\text { e. } \mathrm{CH}_{4}(\mathrm{g})+2 \mathrm{H}_{2} \mathrm{S}(\mathrm{g}) \rightleftharpoons \mathrm{CS}_{2}(\mathrm{g})+4 \mathrm{H}_{2}(\mathrm{g})}\end{array} $$

Write equilibrium constant expressions for these heterogeneous equilibria. a. \(C_{10} \mathrm{H}_{8}(\mathrm{s}) \rightleftharpoons \mathrm{C}_{10} \mathrm{H}_{8}(\mathrm{g})\) b. \(\mathrm{H}_{2} \mathrm{O}(1) \rightleftharpoons \mathrm{H}_{2} \mathrm{O}(\mathrm{g})\) c. \(\mathrm{CaCO}_{3}(\mathrm{s}) \rightleftharpoons \mathrm{CaO}(\mathrm{s})+\mathrm{CO}_{2}(\mathrm{g})\) d. \(\mathrm{C}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(\mathrm{g}) \rightleftharpoons \mathrm{CO}(\mathrm{g})+\mathrm{H}_{2}(\mathrm{g})\) e. \(\mathrm{FeO}(\mathrm{s})+\mathrm{CO}(\mathrm{g}) \rightleftharpoons \mathrm{Fe}(\mathrm{s})+\mathrm{CO}_{2}(\mathrm{g})\)

Challenge Solid iron reacts with chlorine gas to form solid iron(lil chloride (FeCl,). Write the balanced equation and the equilibrium constant expression for the reaction.

Challenge The reaction \(\mathrm{COCl}_{2}(\mathrm{g}) \rightleftharpoons \mathrm{CO}(\mathrm{g})+\mathrm{Cl}_{2}(\mathrm{g})\) reaches equilibrium at 900 \(\mathrm{K}\) . \(K_{\mathrm{eq}}\) is \(8.2 \times 10^{-2} .\) If the equilibrium concentrations of \(\mathrm{CO}\) and \(\mathrm{Cl}_{2}\) are \(0.150 \mathrm{M},\) what is the equilibrium concentration of \(\mathrm{COCl}_{2}\) ?

A Explain how the size of the equilibrium constant relates to the amount of product formed at equilibriu

Compare homogeneous and heterogeneous equilibria.

. List three characteristics a reaction mixture must have if it is to attain a state of chemical equilibriu

Calculate Determine the value of \(K_{\mathrm{eq}}\) at 400 \(\mathrm{K}\) for this equation: \(\mathrm{PCl}_{5}(\mathrm{g}) \rightleftharpoons \mathrm{PCl}_{3}(\mathrm{g})+\mathrm{Cl}_{2}(\mathrm{g})\) if \(\left[\mathrm{PCl}_{5}\right]=0.135 \mathrm{mol} / \mathrm{L},\left[\mathrm{PCl}_{3}\right]=0.550 \mathrm{mol} / \mathrm{L}\) , and \(\left[\mathrm{Cl}_{2}\right]=0.550 \mathrm{mol} / \mathrm{L} .\)

Interpret Data The table below shows the value of the equilibrium constant for a reaction at three different temperatures. At which temperature is the concentration of the products the greatest? Explain your answer $$ \begin{array}{lll}{263 \mathrm{K}} & {273 \mathrm{K}} & {373 \mathrm{K}} \\\ {0.0250} & {0.500} & {4.500}\end{array} $$

A Explain how a system at equilibrium responds to a stress and list factors that can be stresses on an equilibrium system

Decide whether higher or lower temperatures will produce more \(\mathrm{CH}_{3} \mathrm{CHO}\) in the following equilibrium. \(\mathrm{C}_{2} \mathrm{H}_{2}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{g}) \rightleftharpoons \mathrm{CH}_{3} \mathrm{CHO}(\mathrm{g}) \Delta H^{\circ}=-151 \mathrm{k}\)

. Design a concept map that shows ways in which Le Châtelier’s principle can be applied to increase the products in a system at equilibrium and to increase the reactants in such a system

Challenge The K sp of lead carbonate (PbC O 3) is 7.40 × 1 0 -14 at 298 K. What is the solubility of lead carbonate in g/L?

Use \(K_{\text { sp values from Table } 17.3 \text { to calculate the following. }}\) a. [Ag+ \(]\) in a solution of AgBr at equilibrium b. [F- \(]\) in a saturated solution of \(\mathrm{CaF}_{2}\) c. \(\left[\mathrm{Ag}^{+}\right]\) in a solution of \(\mathrm{Ag}_{2} \mathrm{CrO}_{4}\) at equilibrium

Calculate the solubility of \(\mathrm{Ag}_{3} \mathrm{PO}_{4}\left(K_{\mathrm{sp}}=2.6 \times 10^{-18}\right)\)

Challenge The solubility of silver chloride (AgCl) is \(1.86 \times 10^{-4} \mathrm{g} / 100 \mathrm{g}\) of \(\mathrm{H}_{2} \mathrm{O}\) at 298 \(\mathrm{K}\) . Calculate the \(K_{\mathrm{sp}}\) for AgCl.

Use \(K_{\text { sp values from table }} 17.3\) to predict whether a precipitate will form when equal volumes of the following solutions are mixed. a. 0.10\(M \mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}\) and 0.030 \(\mathrm{M} \mathrm{NaF}\) b. 0.25\(M \mathrm{K}_{2} \mathrm{SO}_{4}\) and 0.010 \(\mathrm{M} \mathrm{AgNO}_{3}\)

Challenge Will a precipitate form when 250 \(\mathrm{mL}\) of 0.20 \(\mathrm{M} \mathrm{MgCl}_{2}\) is added to 750 \(\mathrm{mL}\) of 0.0025 \(\mathrm{NaOH}\) ?

Explain how to use the solubility product constant to calculate the solubility of a sparingly soluble ionic compound.

. Describe how the presence of a common ion reduces the solubility of an ionic compound

Explain the difference between \(K_{\mathrm{sp}}\) and \(Q_{\mathrm{sp} . \text { Is } Q_{\mathrm{sp}} \text { an equilibrium constant? }}\)

Calculate The \(K_{s p}\) of magnesium carbonate \(\left(\mathrm{Mg} \mathrm{CO}_{3}\right)\) is \(2.6 \times 10^{-9} .\) What is the solubility of \(\mathrm{Mg} \mathrm{CO}_{3}\) in pure water?

Design an experiment based on solubilities to demonstrate which of two ions, \(\mathrm{Mg}^{2+}\) or \(\mathrm{Pb}^{2+},\) is contained in an aqueous solution. Solubility information about ionic compounds is given in Tables \(R-3\) and \(R-8\) on pages 969 and 974 respectively.

Describe an equilibrium in everyday life that illustrates a state of balance between two opposing processes.

Given the fact that the concentrations of reactants and products are not changing, why is the word dynamic used to describe chemical equilibrium?

Explain how a person bailing out a row boat with a leak could represent a state of physical equilibrium.

Does the following equation represent a homogeneous equilibrium or a heterogeneous equilibrium? Explain. your answer. $$ \mathrm{H}_{2} \mathrm{O}(s) \rightleftharpoons \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) $$

Explain how to write an equilibrium constant expression.

Why should you pay attention to the physical states of reactants and products when writing equilibrium constant expressions?

Why does a numerically large Keq mean that the products are favored in an equilibrium system?

How can an equilibrium system contain small and unchanging amounts of products yet have large amounts of reactants? What can you say about the relative size of \(K\) eq for such an equilibrium?

A system, which contains only molecules as reactants and products, is at equilibrium. Describe what happens to the concentrations of the reactants and products and what happens to individual reactant and product molecules.

Write equilibrium constant expressions for these homogeneous equilibria. $$ \begin{array}{l}{\text { a. } 2 \mathrm{N}_{2} \mathrm{H}_{4}(\mathrm{g})+2 \mathrm{NO}_{2}(\mathrm{g}) \rightleftharpoons 3 \mathrm{N}_{2}(\mathrm{g})+4 \mathrm{H}_{2} \mathrm{O}(\mathrm{g})} \\ {\text { b. } 2 \mathrm{NbCl}_{4}(\mathrm{g}) \rightleftharpoons \mathrm{NbCl}_{3}(\mathrm{g})+\mathrm{NbCl}_{5}(\mathrm{g})}\end{array} $$

Write equilibrium constant expressions for these heterogeneous equilibria. $$ \begin{array}{l}{\text { a. } 2 \mathrm{NaHCO}_{3}(\mathrm{s}) \rightleftharpoons \mathrm{Na}_{2} \mathrm{CO}_{3}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(\mathrm{g})+\mathrm{CO}_{2}(\mathrm{g})} \\ {\text { b. } \mathrm{C}_{6} \mathrm{H}_{6}(1) \rightleftharpoons \mathrm{C}_{6} \mathrm{H}_{6}(\mathrm{g})}\end{array} $$

Heating limestone (CaCO \(_{3}(s) )\) forms quicklime \((\mathrm{CaO}(\mathrm{s}))\) and carbon dioxide gas. Write the equilibrium constant expression for this reversible reaction.

Suppose you have a cube of pure manganese metal measuring 5.25 \(\mathrm{cm}\) on each side. You find that the mass of the cube is 1076.6 \(\mathrm{g}\) . What is the molar concentration of manganese in the cube?

When steam is passed over iron filings, solid iron(III) oxide and gaseous hydrogen are produced in a reversible reaction. Write the balanced chemical equation and the equilibrium constant expression for the reaction, which yields iron(III) oxide and hydrogen gas.

What is meant by a stress on a reaction at equilibrium?

How does Le Châtelier's principle describe an equilibrium's response to a stress?

Why does removing a reactant cause an equilibrium shift to the left?

When an equilibrium shifts to the right, what happens to each of the following? a. the concentration of the reactants b. the concentration of the products

Carbonated Beverages Use Le Châtelier's principle to explain how a shift in the equilibrium \(\mathrm{H}_{2} \mathrm{CO}_{3}(\mathrm{aq}) \rightleftharpoons\) \(\mathrm{H}_{2} \mathrm{O}(1)+\mathrm{CO}_{2}(\mathrm{g})\) causes a soft drink to go flat when its container is left open.

How would each of the following changes affect the equilibrium position of the system used to produce methanol from carbon monoxide and hydrogen? $$ \mathrm{CO}(\mathrm{g})+2 \mathrm{H}_{2}(\mathrm{g}) \rightleftharpoons \mathrm{CH}_{3} \mathrm{OH}(\mathrm{g})+ $$ a. adding \(\mathrm{CO}\) to the system b. cooling the system c. adding a catalyst to the system d. removing \(\mathrm{CH}_{3}\) OH from the system e. decreasing the volume of the system

A liquid solvent for chlorine is poured into a flask in which the following reaction is at equilibrium: \(\mathrm{PCl}_{5}(\mathrm{g}) \rightleftharpoons \mathrm{PCl}_{3}(\mathrm{g})+\mathrm{Cl}_{2}(\mathrm{g})+\) heat. How is the equilibrium affected when some of the chlorine gas dissolves?

Given two reactions at equilibrium: $$ \begin{array}{l}{\text { a. } \mathrm{N}_{2}(\mathrm{g})+3 \mathrm{H}_{2}(\mathrm{g}) \rightleftharpoons 2 \mathrm{NH}_{3}(\mathrm{g})} \\\ {\text { b. } \mathrm{H}_{2}(\mathrm{g})+\mathrm{Cl}_{2}(\mathrm{g}) \rightleftharpoons 2 \mathrm{HCl}(\mathrm{g})}\end{array} $$

Explain how you would regulate the pressure to favor the products in the following equilibrium system. $$ \mathrm{MgCO}_{3}(\mathrm{s}) \rightleftharpoons \mathrm{MgO}(\mathrm{s})+\mathrm{CO}_{2}(\mathrm{g}) $$

Ethylene \(\left(\mathrm{C}_{2} \mathrm{H}_{4}\right)\) reacts with hydrogen to form ethane \(\left(\mathrm{C}_{2} \mathrm{H}_{6}\right) .\) $$ \mathrm{C}_{2} \mathrm{H}_{4}(\mathrm{g})+\mathrm{H}_{2}(\mathrm{g}) \rightleftharpoons \mathrm{C}_{2} \mathrm{H}_{6}(\mathrm{g})+ $$ How would you regulate the temperature of this equilibrium in order to accomplish each of the following? a. increase the yield of ethane b. decrease the concentration of ethylene c. increase the amount of hydrogen in the system

What does it mean to say that two solutions have a common ion? Give an example.

Why are compounds such as sodium chloride usually not given \(K_{\text {eq }}\)values?

Xrays Why is barium sulfate a better choice than barium chloride for adding definition to \(\mathrm{X}\) rays? At \(26^{\circ} \mathrm{C}\) 37.5 \(\mathrm{g}\) of \(\mathrm{BaCl}_{2}\) can be dissolved in 100 \(\mathrm{mL}\) of water.