Which of the following is not true of a voltaic cell?

The electrodes should always be of metals.

The correct answer is option 4. The electrodes in a voltaic cell do not need to be metals.

Let us evaluate each statement to determine which one is not true of a voltaic cell:

1. The electrode at which the oxidation takes place is called the anode:

The statement is true. In a voltaic cell, oxidation occurs at the anode. The anode is where electrons are released by the oxidation reaction, leading to an increase in the oxidation state of the species involved.

2. The electrode at which the reduction takes place is called the cathode:
The statement is true. In a voltaic cell, reduction occurs at the cathode. The cathode is where electrons are gained by the reduction reaction, leading to a decrease in the oxidation state of the species involved.

3. The medium in which the electrodes are dipped should be a solution of an electrolyte:
The statement is true. In a voltaic cell, the electrodes are typically dipped in an electrolyte solution. The electrolyte solution allows for the flow of ions between the electrodes, completing the electrical circuit and enabling the redox reactions to occur.

4. The electrodes should always be of metals:
The statement is true. While metals are commonly used as electrodes in voltaic cells, they are not the only materials that can be used. Non-metal materials, such as carbon (graphite) or conductive polymers, can also be used as electrodes in certain types of voltaic cells. Therefore, this statement is not true.

The statement that is not true of a voltaic cell is The electrodes should always be of metals.

While metals are commonly used as electrodes, they are not the only materials that can be used.