The following picture represents an equilibrium mixture of solid $\mathrm{BaCO}_3$ solid $\mathrm{BaO}$, and gaseous $\mathrm{CO}_2$ obtained as a result of the endothermic decomposition of $\mathrm{BaCO}_3$ : (a) Draw a picture that represents the equilibrium mixture after addition of four more $\mathrm{CO}_2$ molecules. (b) Draw a picture that represents the equilibrium mixture at a higher temperature.

Lactic acid, which builds up in muscle tissue during strenuous exercise, is partially dissociated in aqueous solution: CC(O)C(=O)O Lactic acid Lactate ion (a) Write the equilibrium-constant expression for $K_c$. (b) What is the value of $K_{\mathrm{c}}$ if the extent of dissociation in $0.100 \mathrm{M}$ lactic acid is $3.65 \%$ at $25^{\circ} \mathrm{C}$ ?

The following pictures represent the initial state and the equilibrium state for the reaction of $A_2$ molecules (red) with $B$ atoms (blue) to give $\mathrm{AB}$ molecules: Initial state Equilibrium state (a) Write a balanced chemical equation for the reaction. (b) If the volume of the equilibrium mixture is decreased, will the number of $\mathrm{AB}$ molecules increase, decrease, or remain the same? Explain.

The reaction $\mathrm{A}_2+\mathrm{B} \rightleftharpoons \mathrm{A}+\mathrm{AB}$ has an equilibrium constant $K_c=2$. The following pictures represent reaction mixtures that contain $\mathrm{A}$ atoms (red), $\mathrm{B}$ atoms (blue), and $\mathrm{A}_2$ and $\mathrm{AB}$ molecules: (1) (2) (3) (a) Which reaction mixture is at equilibrium? (b) For those mixtures that are not at equilibrium, will the reaction go in the forward or reverse direction to reach equilibrium? Explain.

The following pictures represent the equilibrium state for three different reactions of the type $A_2+X_2 \rightleftharpoons 2 \mathrm{AX}(X=B$, Coor D):

$$\mathrm{A}_2+\mathrm{B}_2 \rightleftarrows 2 \mathrm{AB} \quad \mathrm{A}_2+\mathrm{C}_2 \rightleftarrows 2 \mathrm{AC} \quad \mathrm{A}_2+\mathrm{D}_2 \rightleftarrows 2 \mathrm{AD}$$

(a) Which reaction has the largest equilibrium constant? (b) Which reaction has the smallest equilibrium constant?

Consider the interconversion of $A$ molecules (red spheres) and $\mathrm{B}$ molecules (blue spheres) according to the reaction $A \rightleftharpoons \mathrm{B}$. Each of the following series of pictures represents a separate experiment in which time increases from left to right:

How many $\mathrm{O}_2$ molecules are drawn into the lungs of an average person with each breath? Assume that the ambient air pressure is $1.00 \mathrm{~atm}$ and the temperature is $25^{\circ} \mathrm{C}$.

The affinity of hemoglobin (Hb) for CO is greater than its affinity for $\mathrm{O}_2$. Use Le Chatelier's principle to predict how $\mathrm{CO}$ affects the equilibrium $\mathrm{Hb}+\mathrm{O}_2 \rightleftharpoons$ $\mathrm{Hb}\left(\mathrm{O}_2\right)$. Suggest a reason for the toxicity of $\mathrm{CO}$.

A platinum catalyst is used in automobile catalytic converters to hasten the oxidation of carbon monoxide:

$$2 \mathrm{CO}(\mathrm{g})+\mathrm{O}_2(\mathrm{~g}) \stackrel{\mathrm{P} t}{\rightleftharpoons} 2 \mathrm{CO}_2(\mathrm{~g}) \quad \Delta H^{\circ}=-566 \mathrm{~kJ}$$

Suppose that you have a reaction vessel containing an equilibrium mixture of $\mathrm{CO}(\mathrm{g}), \mathrm{O}_2(\mathrm{~g})$, and $\mathrm{CO}_2(\mathrm{~g})$. Will the amount of $\mathrm{CO}$ in the equilibrium mixture increase, decrease, or remain the same after each of the following changes? (a) A platinum catalyst is added. (b) The temperature is increased. (c) The pressure is increased by decreasing the volume. (d) The pressure is increased by adding argon gas. (e) The pressure is increased by adding $\mathrm{O}_2$ gas.

The following pictures represent the composition of the equilibrium mixture for the reaction $\mathrm{A}(\mathrm{g})+\mathrm{B}(\mathrm{s}) \rightleftharpoons \mathrm{AB}(\mathrm{g})$ at $400 \mathrm{~K}$ and $500 \mathrm{~K}$ : Is the reaction endothermic or exothermic? Explain using Le Chatelier's principle.

Ethyl acetate, a solvent used in many fingernail-polish removers, is made by the reaction of acetic acid with ethanol:

$$\left.\mathrm{CH}_3 \mathrm{CO}_2 \mathrm{H}(\text { soln })+\mathrm{CH}_3 \mathrm{CH}_2 \mathrm{OH}(\text { soln }) \rightleftharpoons \mathrm{CH}_3 \mathrm{CO}_2 \mathrm{CH}_2 \mathrm{CH}_3(\text { soln })+\mathrm{H}_2 \mathrm{O}(\text { soln }) \quad \Delta H^0=-2.9 \mathrm{k}\right)$$

Acetic acid Ethanol Ethyl acetzte Does the amount of ethyl acetate in an equilibrium mixture increase or decrease when the temperature is increased? How does $K_{\mathrm{c}}$ change when the temperature is decreased? Justify your answers using Le Chatelier's principle.

When air is heated at very high temperatures in an automobile engine, the air pollutant nitric oxide is produced by the reaction

$$\mathrm{N}_2(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g}) \rightleftharpoons 2 \mathrm{NO}(\mathrm{g}) \quad \Delta H^{\circ}=+182.6 \mathrm{~kJ}$$

How does the equilibrium amount of NO vary with an increase in temperature?

The following equilibrium concentrations were measured at $800 \mathrm{~K}$ : $\left[\mathrm{SO}_2\right]=3.0 \times 10^{-3} \mathrm{M} ;\left[\mathrm{O}_2\right]=3.5 \times 10^{-3} \mathrm{M} ;\left[\mathrm{SO}_3\right]=5.0 \times 10^{-2} \mathrm{M}$. Calculate the equilibrium constant at $800 \mathrm{~K}$ for each of the reactions in Problem 13.1.

The following picture represents the equilibrium mixture for the gas-phase reaction $A_2 \rightleftharpoons 2 A$ :

Draw a picture that shows how the concentrations change when the pressure is increased by reducing the volume.