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Chapter 18: Problem 103

What reactions take place at the cathode and the anode when each of the following is electrolyzed? a. molten \(\mathrm{NiBr}_{2}\) b. molten \(\mathrm{AlF}_{3}\) c. molten \(\mathrm{MnI}_{2}\)

Short Answer

Expert verified
During the electrolysis of the given molten compounds: a. For molten NiBr₂, cathode reaction: \(Ni^{2+}(l) + 2e^- \rightarrow Ni(s)\), and anode reaction: \(2Br^-(l) \rightarrow Br_2(g) + 2e^-\). b. For molten AlF₃, cathode reaction: \(Al^{3+}(l) + 3e^- \rightarrow Al(s)\), and anode reaction: \(6F^-(l) \rightarrow 3F_2(g) + 6e^-\). c. For molten MnI₂, cathode reaction: \(Mn^{2+}(l) + 2e^- \rightarrow Mn(s)\), and anode reaction: \(2I^-(l) \rightarrow I_2(g) + 2e^-\).

Step by step solution

01

a. Reactions in electrolysis of molten NiBr₂

First, let's identify the cations and anions in the compound. NiBr₂ contains the cations Ni²⁺ and anions Br⁻. During electrolysis: - Reduction takes place at the cathode. - Oxidation takes place at the anode. Reduction half-reaction at the cathode: \[Ni^{2+}(l) + 2e^- \rightarrow Ni(s)\] Oxidation half-reaction at the anode: \[2Br^-(l) \rightarrow Br_2(g) + 2e^-\]
02

b. Reactions in electrolysis of molten AlF₃

First, let's identify the cations and anions in the compound. AlF₃ contains the cations Al³⁺ and anions F⁻. Reduction half-reaction at the cathode: \[Al^{3+}(l) + 3e^- \rightarrow Al(s)\] Oxidation half-reaction at the anode: \[6F^-(l) \rightarrow 3F_2(g) + 6e^-\]
03

c. Reactions in electrolysis of molten MnI₂

First, let's identify the cations and anions in the compound. MnI₂ contains the cations Mn²⁺ and anions I⁻. Reduction half-reaction at the cathode: \[Mn^{2+}(l) + 2e^- \rightarrow Mn(s)\] Oxidation half-reaction at the anode: \[2I^-(l) \rightarrow I_2(g) + 2e^-\] In summary, during the electrolysis of the given molten compounds, the respective metal cations (Ni²⁺, Al³⁺, and Mn²⁺) get reduced at the cathode, and the respective halogen anions (Br⁻, F⁻, and I⁻) get oxidized at the anode.

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Most popular questions from this chapter

The following standard reduction potentials have been determined for the aqueous chemistry of indium: $$\begin{array}{ll}\mathrm{In}^{3+}(a q)+2 \mathrm{e}^{-} \longrightarrow \operatorname{In}^{+}(a q) & \mathscr{E}^{\circ}=-0.444 \mathrm{~V} \\ \mathrm{In}^{+}(a q)+\mathrm{e}^{-} \longrightarrow \operatorname{In}(s) & \mathscr{E}^{\circ}=-0.126 \mathrm{~V}\end{array}$$ a. What is the equilibrium constant for the disproportionation reaction, where a species is both oxidized and reduced, shown below? $$3 \operatorname{In}^{+}(a q) \longrightarrow 2 \operatorname{In}(s)+\operatorname{In}^{3+}(a q)$$ b. What is \(\Delta G_{\mathrm{f}}^{\circ}\) for \(\mathrm{In}^{+}(a q)\) if \(\Delta G_{\mathrm{f}}^{\circ}=-97.9 \mathrm{~kJ} / \mathrm{mol}\) for \(\mathrm{In}^{3+}(a q)\) ?

The compound with the formula \(\mathrm{TII}_{3}\) is a black solid. Given the following standard reduction potentials, \(\begin{aligned} \mathrm{Tl}^{3+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{Tl}^{+} & & 8^{\circ}=1.25 \mathrm{~V} \\ \mathrm{I}_{3}^{-}+2 \mathrm{e}^{-} \longrightarrow 3 \mathrm{I}^{-} & & \mathscr{C}^{\circ} &=0.55 \mathrm{~V} \end{aligned}\) would you formulate this compound as thallium(III) iodide or thallium(I) triiodide?

An electrochemical cell consists of a nickel metal electrode immersed in a solution with \(\left[\mathrm{Ni}^{2+}\right]=1.0 M\) separated by a porous disk from an aluminum metal electrode immersed in a solution with \(\left[\mathrm{Al}^{3+}\right]=1.0 M .\) Sodium hydroxide is added to the aluminum compartment, causing \(\mathrm{Al}(\mathrm{OH})_{3}(s)\) to precipitate. After precipitation of \(\mathrm{Al}(\mathrm{OH})_{3}\) has ceased, the concentration of \(\mathrm{OH}^{-}\) is \(1.0 \times 10^{-4} M\) and the measured cell potential is \(1.82 \mathrm{~V}\). Calculate the \(K_{\mathrm{sp}}\) value for \(\mathrm{Al}(\mathrm{OH})_{3}\). $$\mathrm{Al}(\mathrm{OH})_{3}(s) \rightleftharpoons \mathrm{Al}^{3+}(a q)+3 \mathrm{OH}^{-}(a q) \quad K_{\mathrm{sp}}=?$$

Consider only the species (at standard conditions) $$\mathrm{Na}^{+}, \mathrm{Cl}^{-}, \mathrm{Ag}^{+}, \mathrm{Ag}, \mathrm{Zn}^{2+}, \mathrm{Zn}, \mathrm{Pb}$$ in answering the following questions. Give reasons for your answers. (Use data from Table 18.1.) a. Which is the strongest oxidizing agent? b. Which is the strongest reducing agent? c. Which species can be oxidized by \(\mathrm{SO}_{4}^{2-}(a q)\) in acid? d. Which species can be reduced by \(\mathrm{Al}(s)\) ?

A factory wants to produce \(1.00 \times 10^{3} \mathrm{~kg}\) barium from the electrolysis of molten barium chloride. What current must be applied for \(4.00 \mathrm{~h}\) to accomplish this?
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