**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 Zn^{2+} + 2 e^{-} |
||

Reduction: |
2 H^{+} + 2 e^{-} H_{2} |

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

anode: |
Zn | | | Zn^{2+}(1.0 M) |

The line notation for the cathode has to indicate that H^{+}
ions are reduced to H_{2} gas on a platinum metal
surface. This can be done as follows.

cathode: |
H^{+}(1.0 M) |
| | H_{2}(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 | | | Zn^{2+}(1.0 M) |
|| | H^{+}(1.0 M) |
| | H_{2}(1 atm) |
| | Pt |

anode | cathode |