Write the half-reactions and the balanced cell reaction for...

Write the half-reactions and the balanced cell reaction for the following galvanic cells. (a) $\operatorname{Cd}(s)\left|\mathrm{Cd}^{2+}(a q) \| \mathrm{Au}^{3+}(a q)\right| \mathrm{Au}(s)$ (b) $\mathrm{Fe}(s)\left|\mathrm{Fe}^{2+}(a q) \| \operatorname{Br}_{2}(a q), \operatorname{Br}^{-}(a q)\right| \operatorname{Pt}(s)$ (c) $\operatorname{Cr}(s)\left|\mathrm{Cr}^{3+}(a q) \| \mathrm{Cu}^{2+}(a q)\right| \mathrm{Cu}(s)$

Write the half-reactions and the balanced cell reaction for the following galvanic cells.
(a) $\operatorname{Cd}(s)\left|\mathrm{Cd}^{2+}(a q) \| \mathrm{Au}^{3+}(a q)\right| \mathrm{Au}(s)$
(b) $\mathrm{Fe}(s)\left|\mathrm{Fe}^{2+}(a q) \| \operatorname{Br}_{2}(a q), \operatorname{Br}^{-}(a q)\right| \operatorname{Pt}(s)$
(c) $\operatorname{Cr}(s)\left|\mathrm{Cr}^{3+}(a q) \| \mathrm{Cu}^{2+}(a q)\right| \mathrm{Cu}(s)$

Key Concepts

Galvanic Cell

A galvanic cell is a type of electrochemical cell that produces electrical energy from a spontaneous redox reaction. It typically consists of two separate half-cells connected by a salt bridge and a conductive external circuit, where oxidation occurs at the anode and reduction at the cathode.

Half-Reactions

Half-reactions are equations that separately describe the oxidation and reduction processes occurring at the anode and cathode, respectively. They illustrate the electron transfer by showing which species loses or gains electrons in the overall redox reaction.

Oxidation and Reduction

Oxidation is the process where a species loses electrons, whereas reduction is the process where a species gains electrons. In the context of a galvanic cell, the oxidation half-reaction occurs at the anode and the reduction half-reaction occurs at the cathode, driving the flow of electrons through the external circuit.

Balancing Redox Reactions

Balancing redox reactions involves ensuring that both mass and charge are conserved. This is done by separately balancing the oxidation and reduction half-reactions—adjusting atoms and charges (often using water, hydrogen ions or hydroxide ions, and electrons)—and then combining them in such a way that the electrons exchanged are equal, resulting in a balanced overall cell reaction.

Electrochemical Cell Components

Understanding the components of an electrochemical cell is crucial; the cell is composed of electrodes (where oxidation and reduction occur), electrolytes (solutions or molten salts that conduct ions), and a salt bridge (which maintains electrical neutrality by allowing ion exchange between the half-cells). Each component plays a vital role in sustaining the redox reaction and generating electrical energy.

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