17.2 Galvanic cells  (Page 3/12)

The cell used an inert platinum wire for the cathode, so the cell notation is

The magnesium electrode is an active electrode    because it participates in the oxidation-reduction reaction. Inert electrodes , like the platinum electrode in [link] , do not participate in the oxidation-reduction reaction and are present so that current can flow through the cell. Platinum or gold generally make good inert electrodes because they are chemically unreactive.

Using cell notation

Write the oxidation and reduction half-reactions and write the reaction using cell notation. Which reaction occurs at the anode? The cathode?

Solution

Cell notation uses the simplest form of each of the equations, and starts with the reaction at the anode. No concentrations were specified so: $\text{Cr}(s)│{\text{Cr}}^{\mathrm{3+}}(aq)║{\text{Cu}}^{\mathrm{2+}}(aq)│\text{Cu}(s).$ Oxidation occurs at the anode and reduction at the cathode.

Using Cell Notation

Consider a galvanic cell consisting of

Write the oxidation and reduction half-reactions and write the reaction using cell notation. Which reaction occurs at the anode? The cathode?

Solution

Cell notation uses the simplest form of each of the equations, and starts with the reaction at the anode. It is necessary to use an inert electrode, such as platinum, because there is no metal present to conduct the electrons from the anode to the cathode. No concentrations were specified so: $\text{Pt}(s)│{\text{Fe}}^{\mathrm{2+}}(aq{\text{), Fe}}^{\mathrm{3+}}(aq)║{\text{MnO}}_4{}^{\text{−}}(aq{\text{), H}}^{\text{+}}(aq{\text{), Mn}}^{\mathrm{2+}}(aq)│\text{Pt}(s).$ Oxidation occurs at the anode and reduction at the cathode.

Check your learning