Consider the standard galvanic cell based on the following halfreactions: $$\begin{array}{r}\mathrm{Cu}^{2+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{Cu} \\ \mathrm{Ag}^{+}+\mathrm{e}^{-} \longrightarrow \mathrm{Ag}\end{array}$$ The electrodes in this cell are \(\mathrm{Ag}(s)\) and \(\mathrm{Cu}(s)\). Does the cell potential increase, decrease, or remain the same when the following changes occur to the standard cell? a. \(\operatorname{CuSO}_{4}(s)\) is added to the copper half-cell compartment (assume no volume change). b. \(\mathrm{NH}_{3}(a q)\) is added to the copper half-cell compartment. [Hint: \(\mathrm{Cu}^{2+}\) reacts with \(\mathrm{NH}_{3}\) to form \(\left.\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}^{2+}(a q) .\right]\) c. \(\mathrm{NaCl}(s)\) is added to the silver half-cell compartment. [Hint: \(\mathrm{Ag}^{+}\) reacts with \(\mathrm{Cl}^{-}\) to form \(\left.\mathrm{AgCl}(s) .\right]\) d. Water is added to both half-cell compartments until the volume of solution is doubled. e. The silver electrode is replaced with a platinum electrode. $$\mathrm{Pt}^{2+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{Pt} \quad \mathscr{E}^{\circ}=1.19 \mathrm{~V}$$

Step by step solution

01

a. Adding CuSO4 to the copper half-cell

When CuSO4 is added to the copper half-cell, the concentration of Cu^{2+} ions will increase in the compartment. According to the Nernst equation, an increase in Cu^{2+} ions concentration will produce an increase in cell potential. Therefore, the cell potential will increase.

02

b. Adding NH3(aq) to the copper half-cell

When NH3 is added to the copper half-cell compartment, the Cu^{2+} ions react with NH3 to form Cu(NH3)_{4}^{2+} ions, decreasing the initial concentration of the Cu^{2+} ions. According to the Nernst equation, a decrease in Cu^{2+} ions concentration will produce a decrease in cell potential. Therefore, the cell potential will decrease.

03

c. Adding NaCl to the silver half-cell

When NaCl is added to the silver half-cell, the Ag^{+} ions will react with Cl^{-} ions to form AgCl(s), which results in decreasing the concentration of Ag^{+} ions in the silver half-cell compartment. According to the Nernst equation, a decrease in Ag^{+} ions concentration will produce a decrease in cell potential. Therefore, the cell potential will decrease.

04

d. Doubling the volume of both half-cell compartments

When the volume of both half-cell compartments is doubled, the concentrations of the ions will be halved. According to the Nernst equation, halving the concentrations in both compartments will not change the cell potential, since the ratio of the ion concentrations remains the same. Therefore, the cell potential remains the same or unchanged.

05

e. Replacing the silver electrode with a platinum electrode

When the silver electrode is replaced with a platinum electrode, the half-reaction involving the silver ions is not directly affected. The cell potential depends on the half-reactions and not the electrode material, as long as the electrode is inert and allows electron transfer. Therefore, the cell potential remains the same.

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