The standard Gibbs energy change for the reaction \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightleftharpoons$$$ \mathrm{CH}_{3} \mathrm{CO}_{2}^{-}(\mathrm{aq})+\mathrm{H}_{3} \mathrm{O}^{+}(\mathrm{aq})$$is \)27.07 \mathrm{kJmol}^{-1}\( at 298 K. Use this thermodynamic quantity to decide in which direction the reaction is spontaneous when the concentrations of \)\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}(\mathrm{aq}), \mathrm{CH}_{3} \mathrm{CO}_{2}^{-}(\mathrm{aq}),\( and \)\mathrm{H}_{3} \mathrm{O}^{+}(\mathrm{aq})\( are \)0.10 \mathrm{M}, 1.0 \times 10^{-3} \mathrm{M},\( and \)1.0 \times 10^{-3} \mathrm{M},$ respectively.

Short Answer

Expert verified
Given the concentrations provided, the reaction \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}(\mathrm{aq})+\mathrm{H}_{2}\mathrm{O}(\mathrm{l}) \rightleftharpoons\) \(\mathrm{CH}_{3} \mathrm{CO}_{2}^{-}(\mathrm{aq})+\mathrm{H}_{3}\mathrm{O}^{+}(\mathrm{aq})\) is spontaneous in the reverse direction.

Step by step solution

01

Determine the Gibbs Energy change under standard conditions

The standard Gibbs energy change(\(\Delta G^o\)) given in the problem is \(27.07 \, kJmol^{-1}.\) We will need to convert this energy into \(Jmol^{-1}\) in order to put it in the correct units for later calculations. So, \(\Delta G^o = 27.07 \times 10^3 \, Jmol^{-1}\).
02

Calculate the Reaction Quotient (Q)

The concentrations given in the problem allow us to determine the reaction quotient Q. For a reaction of the form \(aA + bB \rightleftharpoons cC + dD\), Q is equal to \((C^c \times D^d)/(A^a \times B^b)\). Substituting the provided concentrations into the Q expression yields \(Q = ([CH_{3}CO_{2}^{-}] \times [H_{3}O^{+}])/([CH_{3}CO_{2}H]) = (1.0 \times 10^{-3} \times 1.0 \times 10^{-3})/0.10 = 0.01.\)
03

Calculate the Gibbs Energy change under non-standard conditions

The Gibbs energy change based on the concentrations can be calculated using the relationship \(\Delta G = \Delta G^o + RT \ln Q\), where R is the gas constant (8.314 J/Kmol) and T is the temperature in Kelvin (298 K in this case). Substituting in these values gives us \(\Delta G = 27.07 \times 10^3 + 8.314 \times 298 \times \ln 0.01 = 27.07 \times 10^3 - 4795.21 = 22274.79 \, Jmol^{-1} = 22.27 \, kJmol^{-1}\).
04

Determine the Direction of the Reaction

As the Gibbs energy change calculated is positive, it indicates that the reaction is not spontaneous in the forward direction, but it is in the reverse direction. So, under the given concentrations, the reaction will proceed towards the left, from products to reactants.

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Most popular questions from this chapter

Use ideas from this chapter to explain this famous remark attributed to Rudolf Clausius (1865)\(:^{\prime \prime} \mathrm{Die}\) Energie der Welt ist konstant; die Entropie der Welt strebt einem Maximum zu." ("The energy of the world is constant; the entropy of the world increases toward a maximum.")

At room temperature and normal atmospheric pressure, is the entropy of the universe positive, negative, or zero for the transition of carbon dioxide solid to liquid?

Two equations can be written for the dissolution of \(\mathrm{Mg}(\mathrm{OH})_{2}(\mathrm{s})\) in acidic solution. $$\begin{aligned} \mathrm{Mg}(\mathrm{OH})_{2}(\mathrm{s})+2 \mathrm{H}^{+}(\mathrm{aq}) \rightleftharpoons & \mathrm{Mg}^{2+}(\mathrm{aq})+2 \mathrm{H}_{2} \mathrm{O}(1) \\ & \Delta G^{\circ}=-95.5 \mathrm{kJ} \mathrm{mol}^{-1} \\ (c) Will the solubilities of \(\mathrm{Mg}(\mathrm{OH})_{2}(\mathrm{s})\) in a buffer solution at \(\mathrm{pH}=8.5\) depend on which of the two equations is used as the basis of the calculation? Explain. \frac{1}{2} \mathrm{Mg}(\mathrm{OH})_{2}(\mathrm{s})+\mathrm{H}^{+}(\mathrm{aq}) \rightleftharpoons & \frac{1}{2} \mathrm{Mg}^{2+}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(1) \\ & \Delta G^{\circ}=-47.8 \mathrm{kJ} \mathrm{mol}^{-1} \end{aligned}$$ (a) Explain why these two equations have different \(\Delta G^{\circ}\) values. (b) Will \(K\) for these two equations be the same or different? Explain.

In your own words, define the following symbols: (a) \(\Delta S_{\text {univ }} ;\) (b) \(\Delta G_{f}^{0} ;\) (c) \(K\).

Use data from Appendix D to determine values of \(\Delta G^{\circ}\) for the following reactions at \(25^{\circ} \mathrm{C}\) (a) \(\mathrm{C}_{2} \mathrm{H}_{2}(\mathrm{g})+2 \mathrm{H}_{2}(\mathrm{g}) \longrightarrow \mathrm{C}_{2} \mathrm{H}_{6}(\mathrm{g})\) (b) \(2 \mathrm{SO}_{3}(\mathrm{g}) \longrightarrow 2 \mathrm{SO}_{2}(\mathrm{g})+\mathrm{O}_{2}(\mathrm{g})\) (c) \(\mathrm{Fe}_{3} \mathrm{O}_{4}(\mathrm{s})+4 \mathrm{H}_{2}(\mathrm{g}) \longrightarrow 3 \mathrm{Fe}(\mathrm{s})+4 \mathrm{H}_{2} \mathrm{O}(\mathrm{g})\) (d) \(2 \mathrm{Al}(\mathrm{s})+6 \mathrm{H}^{+}(\mathrm{aq}) \longrightarrow 2 \mathrm{Al}^{3+}(\mathrm{aq})+3 \mathrm{H}_{2}(\mathrm{g})\)

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