Sketch the galvanic cells based on the following overall reactions. Show the direction of electron flow, and identify the cathode and anode. Give the overall balanced equation. Assume that all concentrations are \(1.0 M\) and that all partial pressures are 1.0 atm. a. \(\mathrm{Cr}^{3+}(a q)+\mathrm{Cl}_{2}(g) \rightleftharpoons \mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}(a q)+\mathrm{Cl}^{-}(a q)\) b. \(\mathrm{Cu}^{2+}(a q)+\mathrm{Mg}(s) \rightleftharpoons \mathrm{Mg}^{2+}(a q)+\mathrm{Cu}(s)\)

Short Answer

Expert verified
a. Anode: \(Cl_{2}(g) \rightarrow 2Cl^{-}(a q)\); Cathode: \(2Cr^{3+}(a q) \rightarrow Cr_{2} O_{7}^{2-}(a q)\); Galvanic cell: Cl2 bubbled through Cl⁻ solution (anode), Cr³⁺ solution (cathode) connected by a salt bridge; Overall equation: \(Cr^{3+}(a q)+Cl_{2}(g) \rightleftharpoons Cr_{2} O_{7}^{2-}(a q)+Cl^{-}(a q)\) b. Anode: \(Mg(s) \rightarrow Mg^{2+}(a q) + 2e^-\); Cathode: \(Cu^{2+}(a q) + 2e^- \rightarrow Cu(s)\); Galvanic cell: Mg(s) electrode (anode), Cu²⁺ solution and Cu(s) electrode (cathode) connected by a salt bridge; Overall equation: \(Cu^{2+}(a q)+Mg(s) \rightleftharpoons Mg^{2+}(a q)+Cu(s)\)

Step by step solution

01

a. Cr3+(aq) + Cl2(g) ⇌ Cr2O72−(aq) + Cl−(aq)

1. Identify the half-reactions: We need to break the overall reaction into reduction and oxidation half-reactions: - Oxidation half-reaction: \(\mathrm{Cl}_{2}(g) \rightarrow 2\mathrm{Cl}^{-}(a q)\) - Reduction half-reaction: \(\mathrm{Cr}^{3+}(a q) \rightarrow \frac{1}{2}\mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}(a q)\), multiply by 2 to balance the Cr atoms: \(2\mathrm{Cr}^{3+}(a q) \rightarrow \mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}(a q)\) 2. Identify the anode and cathode: - Anode (oxidation): \(\mathrm{Cl}_{2}(g) \rightarrow 2\mathrm{Cl}^{-}(a q)\) - Cathode (reduction): \(2\mathrm{Cr}^{3+}(a q) \rightarrow \mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}(a q)\) 3. Sketch the galvanic cell: - Anode: Chlorine gas is bubbled through an aqueous solution containing Cl⁻ ions. Electrons flow from the anode to the cathode through an external wire. - Cathode: Chromium(III) ions are present in the aqueous solution to form dichromate ions, Cr2O72-. - Salt bridge: A salt bridge or porous disk connects the two half-cells to maintain charge neutrality. 4. Write the overall balanced equation: The overall balanced equation is given in the problem statement itself: \(\mathrm{Cr}^{3+}(a q)+\mathrm{Cl}_{2}(g) \rightleftharpoons \mathrm{Cr}_{2} \mathrm{O}_{7}^{2-}(a q)+\mathrm{Cl}^{-}(a q)\)
02

b. Cu2+(aq) + Mg(s) ⇌ Mg2+(aq) + Cu(s)

1. Identify the half-reactions: We need to break the overall reaction into reduction and oxidation half-reactions: - Oxidation half-reaction: \(\mathrm{Mg}(s) \rightarrow \mathrm{Mg}^{2+}(a q) + 2e^-\) - Reduction half-reaction: \(\mathrm{Cu}^{2+}(a q) + 2e^- \rightarrow \mathrm{Cu}(s)\) 2. Identify the anode and cathode: - Anode (oxidation): \(\mathrm{Mg}(s) \rightarrow \mathrm{Mg}^{2+}(a q) + 2e^-\) - Cathode (reduction): \(\mathrm{Cu}^{2+}(a q) + 2e^- \rightarrow \mathrm{Cu}(s)\) 3. Sketch the galvanic cell: - Anode: Mg(s) metal electrode is oxidized to Mg²⁺(aq) ions and loses 2 electrons. - Cathode: Cu²⁺(aq) ions are reduced to Cu(s) metal by gaining 2 electrons. - Salt bridge: A salt bridge or porous disk connects the two half-cells to maintain charge neutrality. 4. Write the overall balanced equation: The overall balanced equation is given in the problem statement itself: \(\mathrm{Cu}^{2+}(a q)+\mathrm{Mg}(s) \rightleftharpoons \mathrm{Mg}^{2+}(a q)+\mathrm{Cu}(s)\)

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Most popular questions from this chapter

Calculate \(\mathscr{E}^{\circ}\) values for the following cells. Which reactions are spontaneous as written (under standard conditions)? Balance the equations. Standard reduction potentials are found in Table \(17-1\) a. \(\mathrm{MnO}_{4}^{-}(a q)+\mathrm{I}^{-}(a q) \longrightarrow \mathrm{I}_{2}(a q)+\mathrm{Mn}^{2+}(a q)\) b. \(\mathrm{MnO}_{4}^{-}(a q)+\mathrm{F}^{-}(a q) \longrightarrow \mathrm{F}_{2}(g)+\mathrm{Mn}^{2+}(a q)\)

Under standard conditions, what reaction occurs, if any, when each of the following operations is performed? a. Crystals of \(\mathrm{I}_{2}\) are added to a solution of NaCl. b. \(\mathrm{Cl}_{2}\) gas is bubbled into a solution of NaI. c. A silver wire is placed in a solution of \(\mathrm{CuCl}_{2}\) d. An acidic solution of \(\mathrm{FeSO}_{4}\) is exposed to air. For the reactions that occur, write a balanced equation and calculate \(\mathscr{E}^{\circ}, \Delta G^{\circ},\) and \(K\) at \(25^{\circ} \mathrm{C}\)

Define oxidation and reduction in terms of both change in oxidation number and electron loss or gain.

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. \(2 \mathrm{Cu}^{+}(a q) \rightarrow \mathrm{Cu}^{2+}(a q)+\mathrm{Cu}(s)\) b. \(3 \mathrm{Fe}^{2+}(a q) \rightarrow 2 \mathrm{Fe}^{3+}(a q)+\mathrm{Fe}(s)\) c. \(\mathrm{HClO}_{2}(a q) \rightarrow \mathrm{ClO}_{3}^{-}(a q)+\mathrm{HClO}(a q) \quad\) (unbalanced) Use the half-reactions: \(\mathrm{ClO}_{3}^{-}+3 \mathrm{H}^{+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{HClO}_{2}+\mathrm{H}_{2} \mathrm{O} \quad \mathscr{E}^{\circ}=1.21 \mathrm{V}\) \(\mathrm{HClO}_{2}+2 \mathrm{H}^{+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{HClO}+\mathrm{H}_{2} \mathrm{O} \quad \mathscr{E}^{\circ}=1.65 \mathrm{V}\)

Combine the equations $$ \Delta G^{\circ}=-n F \mathscr{E}^{\circ} \quad \text { and } \quad \Delta G^{\circ}=\Delta H^{\circ}-T \Delta S^{\circ} $$ to derive an expression for \(\mathscr{E}^{\circ}\) as a function of temperature. Describe how one can graphically determine \(\Delta H^{\circ}\) and \(\Delta S^{\circ}\) from measurements of \(\mathscr{E}^{\circ}\) at different temperatures, assuming that \(\Delta H^{\circ}\) and \(\Delta S^{\circ}\) do not depend on temperature. What property would you look for in designing a reference half-cell that would produce a potential relatively stable with respect to temperature?

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