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Chapter 18: Problem 110

What reaction will take place at the cathode and the anode when each of the following is electrolyzed? (Assume standard conditions.) a. 1.0 \(M \mathrm{KF}\) solution b. 1.0\(M \mathrm{CuCl}_{2}\) solution c. 1.0 \( M \mathrm{MgI}_{2}\) solution

Short Answer

Expert verified
For the electrolysis of: a. 1.0 M KF solution: Cathode: \(2H_{2}O + 2e^{-} \rightarrow H_{2} (g) + 2OH^{-}\) ; Anode: \(2H_{2}O \rightarrow O_{2} (g) + 4H^{+} + 4e^{-}\) b. 1.0 M CuCl₂ solution: Cathode: \(Cu^{2+} (aq) + 2e^{-} \rightarrow Cu (s)\) ; Anode: \(2Cl^{-} (aq) \rightarrow Cl_{2} (g) + 2e^{-}\) c. 1.0 M MgI₂ solution: Cathode: \(Mg^{2+} (aq) + 2e^{-} \rightarrow Mg (s)\) ; Anode: \(2I^{-} (aq) \rightarrow I_{2} (s) + 2e^{-}\)

Step by step solution

01

Identify the possible reduction and oxidation half-reactions

We first look at the possible reduction half-reaction happening at the cathode: \(F^{-} (aq) + e^{-} \rightarrow F (s)\) The standard reduction potential is -2.87V. This process would require more energy to reduce the F- to F so it is not feasible. Which means that water will get reduced at the cathode to form hydrogen gas and hydroxide ions: \(2H_{2}O + 2e^{-} \rightarrow H_{2} (g) + 2OH^{-}\) Now let's look at the oxidation half-reaction happening at the anode: \(K(s) \rightarrow K^{+} (aq) + e^{-}\) The potential is -2.93V, meaning it is also not feasible. Instead, water oxidation will occur at the anode: \(2H_{2}O \rightarrow O_{2} (g) + 4H^{+} + 4e^{-}\)
02

Write the overall reaction

Combine the two half-reactions at the cathode and the anode: \(2H_{2}O + 2F^{-} (aq) \rightarrow H_{2} (g) + O_{2} (g) + 2OH^{-} (aq) + 2F^{-} (aq)\) b. Electrolysis of 1.0 M CuCl₂ solution
03

Identify the possible reduction and oxidation half-reactions

Possible reduction half-reaction at the cathode: \(Cu^{2+} (aq) + 2e^{-} \rightarrow Cu (s)\) Possible oxidation half-reactions at the anode: \(2Cl^{-} (aq) \rightarrow Cl_{2} (g) + 2e^{-}\)
04

Write the overall reaction

Combine the two half-reactions at the cathode and the anode: \(Cu^{2+} (aq) + 2Cl^{-} (aq) \rightarrow Cu (s) + Cl_{2} (g)\) c. Electrolysis of 1.0 M MgI₂ solution
05

Identify the possible reduction and oxidation half-reactions

Possible reduction half-reaction at the cathode: \(Mg^{2+} (aq) + 2e^{-} \rightarrow Mg (s)\) Possible oxidation half-reactions at the anode: \(2I^{-} (aq) \rightarrow I_{2} (s) + 2e^{-}\)
06

Write the overall reaction

Combine the two half-reactions at the cathode and the anode: \(Mg^{2+} (aq) + 2I^{-} (aq) \rightarrow Mg (s) + I_{2} (s)\)

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Most popular questions from this chapter

Consider the following galvanic cell: What happens to \(\mathscr{E}\) as the concentration of \(\mathrm{Zn}^{2+}\) is increased? As the concentration of \(\mathrm{Ag}^{+}\) is increased? What happens to \(\mathscr{E}^{\circ}\) in these cases?

Consider a galvanic cell based on the following theoretical half-reactions: $$\begin{array}{ll}{\text {}} & { \mathscr{E}^{\circ}(\mathbf{V}) } \\\ \hline{M^{4+}+4 e^{-} \longrightarrow M} & {0.66} \\ {N^{3+}+3 e^{-} \longrightarrow N} & {0.39}\end{array}$$ What is the value of \(\Delta G^{\circ}\) and \(K\) for this cell?

Balance the following oxidation–reduction reactions that occur in acidic solution using the half-reaction method. a. $\mathrm{Cr}(s)+\mathrm{NO}_{3}^{-}(a q) \rightarrow \mathrm{Cr}^{3+}(a q)+\mathrm{NO}(g)$ b. $\mathrm{CH}_{3} \mathrm{OH}(a q)+\mathrm{Ce}^{4+}(a q) \rightarrow \mathrm{CO}_{2}(a q)+\mathrm{Ce}^{3+}(a q)$ c. $\mathrm{SO}_{3}^{2-}(a q)+\mathrm{MnO}_{4}^{-}(a q) \rightarrow \mathrm{SO}_{4}^{2-}(a q)+\mathrm{Mn}^{2+}(a q)$

An electrochemical cell is set up using the following unbalanced reaction: $$\mathrm{M}^{a+}(a q)+\mathrm{N}(s) \longrightarrow \mathrm{N}^{2+}(a q)+\mathrm{M}(s)$$ The standard reduction potentials are: $$\mathrm{M}^{a+}+a \mathrm{e}^{-} \longrightarrow \mathrm{M} \quad \mathscr{E}^{\circ}=0.400 \mathrm{V}$$ $$\mathrm{N}^{2+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{N} \quad \mathscr{E}^{\circ}=0.240 \mathrm{V}$$ The cell contains 0.10\(M \mathrm{N}^{2+}\) and produces a voltage of 0.180 \(\mathrm{V}\) . If the concentration of \(\mathrm{M}^{a+}\) is such that the value of the reaction quotient \(Q\) is \(9.32 \times 10^{-3},\) calculate \(\left[\mathrm{M}^{a+}\right] .\) Calculate \(w_{\text { max }}\) for this electrochemical cell.

Which of the following statements concerning corrosion is(are) true? For the false statements, correct them. a. Corrosion is an example of an electrolytic process. b. Corrosion of steel involves the reduction of iron coupled with the oxidation of oxygen. c. Steel rusts more easily in the dry (arid) Southwest states than in the humid Midwest states. d. Salting roads in the winter has the added benefit of hindering the corrosion of steel. e. The key to cathodic protection is to connect via a wire a metal more easily oxidized than iron to the steel surface to be protected.
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