Practice Problem 7

Write the line notation for the cell shown in the figure below.



The cell is based on the following half-reactions.

Oxidation:     Zn ---> Zn2+ + 2 e-
Reduction:     2 H+ + 2 e- ---> H2

Since we list the reactants before the products in a half-cell, we write the following line notation for the anode.

anode:   Zn | Zn2+(1.0 M)

The line notation for the cathode has to indicate that H+ ions are reduced to H2 gas on a platinum metal surface. This can be done as follows.

cathode:   H+(1.0 M) | H2(1 atm) | Pt

Since line notation is read in the direction in which electrons flow, we place the notation for the anode before the cathode, as follows.

Zn | Zn2+(1.0 M) || H+(1.0 M) | H2(1 atm) | Pt
    anode   cathode