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Chapter 19: Problem 13

Indicate whether each statement is true or false. (a) A reaction that is spontaneous in one direction will be nonspontaneous in the reverse direction under the same reaction conditions. (b) All spontaneous processes are fast. (c) Most spontaneous processes are reversible. (d) An isothermal process is one in which the system loses no heat. (e) The maximum amount of work can be accomplished by an irreversible process rather than a reversible one.

Short Answer

Expert verified
(a) True (b) False (c) False (d) False (e) False

Step by step solution

01

(a) Spontaneous Reaction in One Direction and Nonspontaneous in the Reverse Direction

For a reaction to be spontaneous, it should have a negative Gibbs free energy (ΔG). When the reaction reverses, the sign of ΔG also reverses. So, if the forward reaction is spontaneous (ΔG < 0), the reverse reaction will have ΔG > 0, which means the reverse reaction is nonspontaneous. Therefore, the statement is \(True\).
02

(b) Spontaneity and Speed of Processes

Spontaneity of a process just depends on the initial and final states, and does not account for the speed of the process. It is determined by the Gibbs free energy (ΔG). Processes with negative ΔG are spontaneous, but it does not necessarily mean they are fast. Some spontaneous processes can be quite slow. Therefore, the statement is \(False\).
03

(c) Spontaneity and Reversibility of Processes

Spontaneity does not directly relate to the reversibility of a process. Spontaneity is defined by the Gibbs free energy (ΔG), and for a process to be reversible, it should be in equilibrium, meaning there should be no net change in free energy. The statement that most spontaneous processes are reversible is not correct. Therefore, the statement is \(False\).
04

(d) Isothermal Process and Heat Loss

An isothermal process is a process that occurs at a constant temperature. It does not necessarily mean that the system loses no heat. During an isothermal process, heat can be exchanged between the system and its surroundings, as it should maintain a constant temperature. Therefore, the statement is \(False\).
05

(e) Maximum Work Accomplished by Irreversible or Reversible Processes

The maximum amount of work that can be accomplished by a system is when the process is reversible. This is because, during a reversible process, the system is always near equilibrium, and the work done by the system is maximized in small increments. In contrast, an irreversible process deviates from equilibrium and results in less work being done by the system due to losses caused by factors such as friction and turbulence. Therefore, the statement is \(False\).

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Most popular questions from this chapter

The normal boiling point of \(n\) -octane $\left(\mathrm{C}_{8} \mathrm{H}_{18}\right)\( is \)125^{\circ} \mathrm{C}$. (a) Is the condensation of gaseous \(n\) -octane to liquid \(n\) -octane an endothermic or exothermic process? (b) In what temperature range is the boiling of \(n\) -octane a spontaneous process? (c) In what temperature range is it a nonspontaneous process? (d) Is there any temperature at which liquid \(n\) -octane and gaseous \(n\) -octane are in equilibrium? Explain.

Carbon disulfide \(\left(C S_{2}\right)\) is a toxic, highly flammable substance. The following thermodynamic data are available for \(\mathrm{CS}_{2}(I)\) and \(\mathrm{CS}_{2}(g)\) at \(298 \mathrm{~K}\) \begin{tabular}{lcc} \hline & \(\Delta H_{i}(\mathrm{k} / \mathrm{mol})\) & $\Delta G_{i}^{\prime}(\mathrm{kJ} / \mathrm{mol})$ \\ \hline\(C S_{2}(l)\) & 89.7 & 65.3 \\ \(C S_{2}(g)\) & 117.4 & 67.2 \\ \hline \end{tabular} (a) Draw the Lewis structure of the molecule. What do you predict for the bond order of the \(\mathrm{C}-\mathrm{S}\) bonds? \((\mathbf{b})\) Use the VSEPR method to predict the structure of the \(\mathrm{CS}_{2}\) molecule. (c) Liquid \(\mathrm{CS}_{2}\) burns in \(\mathrm{O}_{2}\) with a blue flame, forming \(\mathrm{CO}_{2}(g)\) and \(\mathrm{SO}_{2}(g)\). Write a balanced equation for this reaction. (d) Using the data in the preceding table and in Appendix \(C,\) calculate \(\Delta H^{\circ}\) and \(\Delta G^{\circ}\) for the reaction in part \((c) .\) Is the reaction exothermic? Is it spontaneous at \(298 \mathrm{~K} ?\) (e) Use the data in the table to calculate \(\Delta S^{\circ}\) at $298 \mathrm{~K}\( for the vaporization of \)\mathrm{CS}_{2}(I) .$ Is the sign of \(\Delta S^{\circ}\) as you would expect for a vaporization? (f) Using data in the table and your answer to part (e), estimate the boiling point of \(\mathrm{CS}_{2}(l)\). Do you predict that the substance will be a liquid or a gas at \(298 \mathrm{~K}\) and \(101.3 \mathrm{kPa}\) ?

An ice cube with a mass of \(25 \mathrm{~g}\) at \(-18{ }^{\circ} \mathrm{C}\) (typical freezer temperature) is dropped into a cup that holds $250 \mathrm{~mL}\( of hot water, initially at \)85^{\circ} \mathrm{C}$. What is the final temperature in the cup? The density of liquid water is $1.00 \mathrm{~g} / \mathrm{mL}\(; the specific heat capacity of ice is \)2.03 \mathrm{~J} / \mathrm{g}{ }^{\circ} \mathrm{C} ;$ the specific heat capacity of liquid water is \(4.184 \mathrm{~J} / \mathrm{g}-\mathrm{K} ;\) the enthalpy of fusion of water is \(6.01 \mathrm{~kJ} / \mathrm{mol}\).

(a) For each of the following reactions, predict the sign of \(\Delta H^{*}\) and \(\Delta S^{\circ}\) without doing any calculations. (b) Based on your general chemical knowledge, predict which of these reactions will have \(K>1\) at \(25^{\circ} \mathrm{C} .(\mathbf{c})\) In each case, indicate whether \(K\) should increase or decrease with increasing temperature. (i) \(2 \mathrm{Fe}(s)+\mathrm{O}_{2}(g) \rightleftharpoons 2 \mathrm{FeO}(s)\) (ii) \(\mathrm{Cl}_{2}(g) \rightleftharpoons 2 \mathrm{Cl}(g)\) (iii) $\mathrm{NH}_{4} \mathrm{Cl}(s) \rightleftharpoons \mathrm{NH}_{3}(g)+\mathrm{HCl}(g)$ (iv) $\mathrm{CO}_{2}(\mathrm{~g})+\mathrm{CaO}(s) \rightleftharpoons \mathrm{CaCO}_{3}(s)$

The reaction $$ \mathrm{SO}_{2}(g)+2 \mathrm{H}_{2} \mathrm{~S}(g) \rightleftharpoons 3 \mathrm{~S}(s)+2 \mathrm{H}_{2} \mathrm{O}(g) $$ is the basis of a suggested method for removal of \(\mathrm{SO}_{2}\) from power-plant stack gases. The standard free energy of each substance is given in Appendix C. (a) What is the equilibrium constant for the reaction at $298 \mathrm{~K} ?(\mathbf{b})$ In principle, is this reaction a feasible method of removing \(\mathrm{SO}_{2}\) ? (c) If \(P_{5 \mathrm{O}_{2}}=P_{\mathrm{H}_{2}}\) s and the vapor pressure of water is \(3.33 \mathrm{kPa}\), calculate the equilibrium \(\mathrm{SO}_{2}\) pressure in the system at \(298 \mathrm{~K}\). (d) Would you expect the process to be more or less effective at higher temperatures?
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