Question

Draw a labelled diagram of Daniell cell and show

1. electrodes working as anode and cathode and their polarity;
2. direction of flow of electrons and direction of flow of conventional current;
3. half cell reactions and the net cell reaction.

Answer 1

i. A Daniel cell is shown in the diagram. The zinc electrode serves as the anode in a Daniel cell and is connected to the battery’s negative end. At the anode, oxidation takes place. Copper metal serves as the cathode and is connected to the battery’s positive terminal. At the cathode, reduction takes place. The anode is negatively polarised, while the cathode is positively polarised.

ii. The diagram shows a Daniel cell, where oxidation takes place at the zinc electrode, which serves as the anode. Because it is connected to the battery’s positive end, the copper electrode serves as the cathode. At the cathode, reduction takes place.

Reaction at anode:

\[\ce{Zn -> Zn^2+ + 2e-}\]

Reaction at cathode:

\[\ce{Cu^2+ + 2e- -> Cu}\]

After being released from the solution, zinc ions leave behind electrons at the anode. These electrons flow along the outer circuit to the cathode, where copper ions arrive, take up electrons, and then discharge. Current flows from right to left because the direction of current flow is always the opposite of that of electron movement.

iii. The Daniel cell is an example of a simple electrochemical cell. Each half-cell reaction can be represented as

Half-cell reaction at the anode:

\[\ce{Zn -> Zn^2+ + 2e-}\]

Half-cell reaction at the cathode:

\[\ce{Cu^2+ + 2e- -> Cu}\]

Net cell reaction:

\[\ce{Zn + Cu^2+ -> Zn^2+ + Cu}\]