Consider the cell described below: $$\text { Al }\left|\mathrm{Al}^{3+}(1.00 M)\right|\left|\mathrm{Pb}^{2+}(1.00 M)\right| \mathrm{Pb}$$ Calculate the cell potential after the reaction has operated long enough for the [Al \(^{3+} ]\) to have changed by 0.60 \(\mathrm{mol} / \mathrm{L}\) . (Assume \(T=25^{\circ} \mathrm{C} .\)

Short Answer

Expert verified
The initial cell potential is \(E_{cell}^0 = 1.53 \ V\). After the reaction has operated long enough, the new concentrations are \([Al^{3+}]' = 0.40 \ M\) and \([Pb^{2+}]' = 1.40 \ M\). Using the Nernst equation, we can calculate the new cell potential: \(E_{cell} = 1.53 V - \frac{(8.314 J/(mol·K))(298 K)}{6(96485 C/mol)} \ln\frac{(1.40)^2(0.40)^3}{(1.00)^2(1.00)^3}\), which yields \(E_{cell} \approx 1.36 \ V\).

Step by step solution

01

Calculate the initial cell potential

First, we need to determine the initial cell potential of the galvanic cell. To do this, we'll need to use the standard reduction potentials for the half-cell reactions. The standard reduction potentials are: $$E^0_{Al^{3+}/Al} = -1.66 \ V$$ $$E^0_{Pb^{2+}/Pb} = -0.13 \ V$$ Now we can calculate the initial cell potential using the equation: $$E_{cell}^{0} = E_{cathode}^{0} - E_{anode}^{0}$$ $$E_{cell}^{0} = (-0.13V) - (-1.66V)$$
02

Calculate the new concentrations

We are given that the change in the concentration of Al^{3+} is 0.60 mol/L, and we need to find the new concentrations after the reaction has operated long enough. First, calculate the moles of electrons, \(n_e\), that would be required by the change in the concentration of \(Al^{3+}\): $$n_e = 3 \times \Delta [Al^{3+}] = 3 \times 0.60 \ mol$$ Now we can calculate the new concentration of \(Pb^{2+}\) by considering the stoichiometry of the reaction: $$\Delta[Pb^{2+}] = \frac{2}{3} \times \Delta[Al^{3+}] = \frac{2}{3} \times 0.60 \ mol$$ Lastly, we can calculate the new concentrations of \(Al^{3+}\) and \(Pb^{2+}\): $$[Al^{3+}'] = 1.00 \ M - 0.60 \ M$$ $$[Pb^{2+}'] = 1.00 \ M + \frac{0.60 \ M}{3} \times 2$$
03

Use the Nernst Equation to find the cell potential

Now we'll apply the Nernst equation to calculate the cell potential after the reaction has operated long enough: $$E_{cell} = E_{cell}^0 - \frac{RT}{nF} \ln Q$$ where R is the ideal gas constant, T is the temperature in Kelvin, n is the number of moles of electrons transferred per reaction, F is Faraday's constant, and Q is the reaction quotient given by: $$Q = \frac{[Pb^{2+}'][Al^{3+}]^3}{[Al^{3+}'][Pb^{2+}]^2}$$ Plug in the values of the constants and the new concentrations of \(Al^{3+}\) and \(Pb^{2+}\), and calculate the new cell potential, \(E_{cell}\).

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Most popular questions from this chapter

Consider the cell described below: $$\mathrm{Zn}\left|\mathrm{Zn}^{2+}(1.00 M)\right|\left|\mathrm{Ag}^{+}(1.00 M)\right| \mathrm{Ag}$$ Calculate the cell potential after the reaction has operated long enough for the \(\left[\mathrm{Zn}^{2+}\right]\) to have changed by 0.20 $\mathrm{mol} / \mathrm{L}\( . (Assume \)T=25^{\circ} \mathrm{C} . )$

Consider a concentration cell that has both electrodes made of some metal M. Solution A in one compartment of the cell contains 1.0\(M \mathrm{M}^{2+} .\) Solution \(\mathrm{B}\) in the other cell compartment has a volume of 1.00 L. At the beginning of the experiment 0.0100 mole of \(\mathrm{M}\left(\mathrm{NO}_{3}\right)_{2}\) and 0.0100 mole of \(\mathrm{Na}_{2} \mathrm{SO}_{4}\) are dissolved in solution \(\mathrm{B}\) (ignore volume changes), where the reaction $$\mathrm{M}^{2+}(a q)+\mathrm{SO}_{4}^{2-}(a q) \rightleftharpoons \mathrm{MSO}_{4}(s)$$ occurs. For this reaction equilibrium is rapidly established, whereupon the cell potential is found to be 0.44 \(\mathrm{V}\) at \(25^{\circ} \mathrm{C} .\) Assume that the process $$\mathrm{M}^{2+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{M}$$ has a standard reduction potential of \(-0.31 \mathrm{V}\) and that no other redox process occurs in the cell. Calculate the value of \(K_{\mathrm{sp}}\) for \(\mathrm{MSO}_{4}(s)\) at \(25^{\circ} \mathrm{C} .\)

A disproportionation reaction involves a substance that acts as both an oxidizing and a reducing agent, producing higher and lower oxidation states of the same element in the products. Which of the following disproportionation reactions are spontaneous under standard conditions? Calculate $\Delta G^{\circ}\( and \)K\( at \)25^{\circ} \mathrm{C}$ for those reactions that are spontaneous under standard conditions. a. $2 \mathrm{Cu}^{+}(a q) \longrightarrow \mathrm{Cu}^{2+}(a q)+\mathrm{Cu}(s)$ b. $3 \mathrm{Fe}^{2+}(a q) \longrightarrow 2 \mathrm{Fe}^{3+}(a q)+\mathrm{Fe}(s)$ c. $\mathrm{HClO}_{2}(a q) \longrightarrow \mathrm{ClO}_{3}^{-}(a q)+\mathrm{HClO}(a q) \quad$ (unbalanced) Use the half-reactions: $\mathrm{ClO}_{3}^{-}+3 \mathrm{H}^{+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{HClO}_{2}+\mathrm{H}_{2} \mathrm{O} \quad \mathscr{E}^{\circ}=1.21 \mathrm{V}$ $\mathrm{HClO}_{2}+2 \mathrm{H}^{+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{HClO}+\mathrm{H}_{2} \mathrm{O} \quad \mathscr{E}^{\circ}=1.65 \mathrm{V}$

The overall reaction in the lead storage battery is $\mathrm{Pb}(s)+\mathrm{PbO}_{2}(s)+2 \mathrm{H}^{+}(a q)+2 \mathrm{HSO}_{4}^{-}(a q) \longrightarrow$ \(2 \mathrm{PbSO}_{4}(s)+2 \mathrm{H}_{2} \mathrm{O}(l)\) Calculate \(\mathscr{E}\) at \(25^{\circ} \mathrm{C}\) for this battery when \(\left[\mathrm{H}_{2} \mathrm{SO}_{4}\right]=4.5 \mathrm{M}\), that is, $\left[\mathrm{H}^{+}\right]=\left[\mathrm{HSO}_{4}^{-}\right]=4.5 \mathrm{M} . \mathrm{At} 25^{\circ} \mathrm{C}, \mathscr{E}^{\circ}=2.04 \mathrm{V}$ for the lead storage battery.

Calculate \(\mathscr{E}^{\circ}\) and \(\Delta G^{\circ}\) for the reaction $$2 \mathrm{H}_{2} \mathrm{O}(l) \longrightarrow 2 \mathrm{H}_{2}(g)+\mathrm{O}_{2}(g)$$ at 298 \(\mathrm{K}\) . Using thermodynamic data in Appendix \(4,\) estimate \(\mathscr{E}^{\circ}\) and \(\Delta G^{\circ}\) at \(0^{\circ} \mathrm{C}\) and $90 .^{\circ} \mathrm{C}\( . Assume \)\Delta H^{\circ}\( and \)\Delta S^{\circ}$ do not depend on temperature.

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