Which of the following statement(s) is/are true? a. Copper metal can be oxidized by \(\mathrm{Ag}^{+}\) (at standard conditions). b. In a galvanic cell the oxidizing agent in the cell reaction is present at the anode. c. In a cell using the half reactions \(\mathrm{Al}^{3+}+3 \mathrm{e}^{-} \longrightarrow \mathrm{Al}\) and \(\mathrm{Mg}^{2+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{Mg}\), aluminum functions as the anode. d. In a concentration cell electrons always flow from the compartment with the lower ion concentration to the compartment with the higher ion concentration. e. In a galvanic cell the negative ions in the salt bridge flow in the same direction as the electrons.

To determine if copper metal can be oxidized by \(\mathrm{Ag}^{+}\) at standard conditions, we can refer to standard reduction potentials. The standard reduction potential for copper is: $$\mathrm{Cu}^{2+} + 2\mathrm{e}^- \longrightarrow \mathrm{Cu}\;\;\;\;\; E^0 = +0.34\,\mathrm{V}$$ The standard reduction potential for silver is: $$\mathrm{Ag}^{+} + \mathrm{e}^- \longrightarrow \mathrm{Ag}\;\;\;\;\; E^0 = +0.80\,\mathrm{V}$$ Since the silver ion has a higher reduction potential, it can oxidize copper metal under standard conditions. So, statement a is true.

In a galvanic cell, the oxidizing agent is the substance that causes the oxidation of another substance by accepting electrons. At the anode, the half-cell reaction that takes place is oxidation, and electrons are released. The oxidizing agent is present at the cathode, where it accepts these electrons and undergoes reduction. Since the statement states that the oxidizing agent is present at the anode, statement b is false.

To analyze this statement, we can look at the reduction potentials of the aluminum and magnesium half reactions. The standard reduction potentials are: $$\mathrm{Al}^{3+} + 3\mathrm{e}^- \longrightarrow \mathrm{Al}\;\;\;\;\; E^0 = -1.66\,\mathrm{V}$$ $$\mathrm{Mg}^{2+} + 2\mathrm{e}^- \longrightarrow \mathrm{Mg}\;\;\;\;\; E^0 = -2.37\,\mathrm{V}$$ In a galvanic cell, the half-reaction with the higher reduction potential will act as the reduction half-cell (cathode), and the half-reaction with the lower reduction potential will act as the oxidation half-cell (anode). In this case, aluminum has a higher reduction potential than magnesium, implying that aluminum would act as a cathode and not the anode. Therefore, statement c is false.

In a concentration cell, two half-cells with different concentrations of the same ion are connected to produce an electric current. This spontaneous redox reaction is a result of the chemical potential difference between the two half-cells. The electrons in a concentration cell flow from the compartment with lower potential (lower ion concentration) to the compartment with the higher potential (higher ion concentration). An overall reaction with a positive cell potential occurs, which drives the cell. Therefore, statement d is true.

In a galvanic cell, a salt bridge is used to maintain the neutrality of charges in the two half-cells. The negative ions in the salt bridge (anions) move towards the half-cell where positive ions accumulate, which occurs at the cathode. This direction is opposite to the flow of electrons, as electrons flow from the anode to the cathode through the external circuit. Therefore, statement e is false. In conclusion, statements a and d are true, while statements b, c, and e are false.