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

Write the half-reactions and the balanced cell reaction for the following galvanic cells. $$ \begin{array}{l} \text { (a) } \mathrm{Zn}(s)\left|\mathrm{Zn}^{2+}(a q) \| \mathrm{Cr}^{3+}(a q)\right| \mathrm{Cr}(s) \\ \text { (b) } \mathrm{Pb}(s), \mathrm{PbSO}_{4}(s) \mid \mathrm{HSO}_{4}^{-}(a q) \| \\ \mathrm{H}^{+}(a q), \mathrm{HSO}_{4}^{2-}(a q) \mid \mathrm{PbO}_{2}(s), \mathrm{PbSO}_{4}(s) \\ \text { (c) } \mathrm{Mg}(s)\left|\mathrm{Mg}^{2+}(a q) \| \mathrm{Sn}^{2+}(a q)\right| \mathrm{Sn}(s) \end{array} $$

Write the half-reactions and the balanced cell reaction for the following galvanic cells.
$$
\begin{array}{l}
\text { (a) } \mathrm{Zn}(s)\left|\mathrm{Zn}^{2+}(a q) \| \mathrm{Cr}^{3+}(a q)\right| \mathrm{Cr}(s) \\
\text { (b) } \mathrm{Pb}(s), \mathrm{PbSO}_{4}(s) \mid \mathrm{HSO}_{4}^{-}(a q) \| \\
\mathrm{H}^{+}(a q), \mathrm{HSO}_{4}^{2-}(a q) \mid \mathrm{PbO}_{2}(s), \mathrm{PbSO}_{4}(s) \\
\text { (c) } \mathrm{Mg}(s)\left|\mathrm{Mg}^{2+}(a q) \| \mathrm{Sn}^{2+}(a q)\right| \mathrm{Sn}(s)
\end{array}
$$

Key Concepts

Galvanic Cell

A galvanic cell, also known as a voltaic cell, is an electrochemical cell that converts chemical energy into electrical energy through spontaneous redox reactions. It is composed of two half-cells, each with its own electrode and electrolyte, connected by a salt bridge or porous membrane that allows ionic conduction while keeping the solutions separate.

Half-Reactions

Half-reactions represent the individual oxidation and reduction processes that occur at the separate electrodes of an electrochemical cell. Writing these reactions separately helps in the understanding and balancing of the overall redox reaction by focusing on the electron transfer taking place in each half-cell.

Oxidation and Reduction

In any redox process, oxidation refers to the loss of electrons, while reduction involves the gain of electrons. In a galvanic cell, the anode is the site of oxidation (electron loss) and the cathode is the site of reduction (electron gain), and these processes must have equal numbers of electrons transferred when combined to form the balanced overall reaction.

Cell Notation

Cell notation is a shorthand notation to represent the components, reactions, and direction of electron flow in an electrochemical cell. It lists the reactants and products for both half-cells separated by a double vertical line, which indicates the barrier (like a salt bridge) between the two half-cells.

Balancing Redox Reactions

Balancing redox reactions involves ensuring that both mass and charge are conserved. This usually requires balancing the atoms involved in the redox process and adjusting the electrons lost and gained so that they cancel out when the half-reactions are combined into the overall cell reaction.

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