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 $\mathrm{Al}^{3+}+3 \mathrm{e}^{-} \longrightarrow$ 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.

Copper metal can be oxidized by \(\mathrm{Ag}^{+}\) (at standard conditions). If a redox reaction occurs, the reaction will involve the transfer of electrons. We can determine the feasibility of this reaction by comparing the reduction potentials of the two species in question. The reduction potential of \(\mathrm{Cu}^{2+}\) is \(+0.34V\) and the reduction potential for \(\mathrm{Ag}^{+}\) is \(+0.80V\). Since the reduction potential of \(\mathrm{Ag}^{+}\) is more positive, this reaction is thermodynamically possible, with \(\mathrm{Cu}\) being oxidized to \(\mathrm{Cu}^{2+}\) and \(\mathrm{Ag}^{+}\) being reduced to \(\mathrm{Ag}\). Therefore, statement a is true.

In a galvanic cell, the oxidizing agent in the cell reaction is present at the anode. In a galvanic cell, the anode is where the oxidation half-reaction occurs, and the cathode is where the reduction half-reaction takes place. The oxidizing agent accepts electrons in the process, so it undergoes reduction. Since reduction takes place at the cathode, the oxidizing agent is present at the cathode. Therefore, statement b is false.

In a cell using the half reactions \(\mathrm{Al}^{3+}+3 \mathrm{e}^{-} \longrightarrow\) Al and \(\mathrm{Mg}^{2+}+2 \mathrm{e}^{-} \longrightarrow \mathrm{Mg}\), aluminum functions as the anode. Here, we have two half-reactions: one involving \(\mathrm{Al}^{3+}\) and one involving \(\mathrm{Mg}^{2+}\). In a galvanic cell, the half-cell with a more negative reduction potential functions as the anode (where oxidation occurs). The standard reduction potentials for \(\mathrm{Al}^{3+}\) and \(\mathrm{Mg}^{2+}\) are \(-1.66V\) and \(-2.37V\), respectively. Since the reduction potential of \(\mathrm{Mg}^{2+}\) is more negative, the anode in this cell will consist of magnesium undergoing oxidation to \(\mathrm{Mg}^{2+}\). Therefore, statement c is false.

In a concentration cell, electrons always flow from the compartment with the lower ion concentration to the compartment with the higher ion concentration. In a concentration cell, the flow of electrons is driven by concentration differences, producing a voltage. The anode compartment will have a higher ion concentration and will undergo oxidation, releasing electrons into the external circuit. The cathode compartment will have a lower ion concentration and will undergo reduction, accepting these electrons. Electrons flow from the anode to the cathode, so this statement is true.

In a galvanic cell, the negative ions in the salt bridge flow in the same direction as the electrons. The purpose of the salt bridge in a galvanic cell is to maintain overall electrical neutrality. As electrons flow from the anode to the cathode, a cation from the salt bridge must migrate towards the cathode compartment to balance the charge. As electrons flow back from the cathode to the anode, an anion from the salt bridge migrates towards the anode compartment to balance the charge. Therefore, the movement of anions in the salt bridge is opposite to the direction of electron flow and statement e is false. In summary, statements a and d are true, while statements b, c, and e are false.