Practice Problem 7
Write the line notation for the cell shown in the figure below.
Answer
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 | |||||||
