The anode of an electrolytic cell must be connected to which terminal- positive or negative-of the power source?

Understanding what happens at the electrodes in an electrolytic cell is essential for grasping the whole electrolysis process. In such a cell, two chemical reactions occur at the electrodes: oxidation and reduction.

Oxidation at the Anode

At the anode, oxidation takes place. This involves the loss of electrons by atoms or ions. It's easy to remember this if you think of the phrase 'An Ox', as a mnemonic for Anode Oxidation. During this process, the substance at the anode releases electrons, which then travel through the circuit.

Reduction at the Cathode

On the flip side, at the cathode, reduction occurs. This is the gain of electrons, and you can remember it with 'Red Cat' for Reduction at the Cathode. Here, the incoming electrons from the anode are accepted by atoms or ions, which typically result in the substance at the cathode gaining electrons and being reduced.

These processes are crucial because they transform the material or substances at both electrodes. For instance, in the electrolysis of water, oxygen gas is produced at the anode through oxidation, and hydrogen gas is produced at the cathode through reduction.

The flow of electrons is the backbone of the electrolysis process. Electrolysis is, in essence, the movement of electrons through a conductor to facilitate a non-spontaneous chemical reaction.

Direction of Electron Flow

In an electrolytic cell, electrons are forced by an external power source (like a battery) to move from the negative terminal, through the external circuit, then into the cell at the cathode, where they cause reduction. They then exit the cell at the anode and return to the positive terminal of the power source. This movement creates the conditions necessary for electrolysis to occur.

To visualize the electron flow better, imagine the external power source as a pump that ‘pushes’ electrons through the circuit, supplying energy to drive the reactions at the electrodes.

The circuit current in electrolysis describes the flow of electrical charge through the system provided by the external power source, which is integral to initiating and sustaining the chemical reactions at the electrodes.

The Role of the Power Source

The power source, such as a battery or a power supply unit, is crucial as it provides a constant flow of direct current (DC) to the circuit. The positive terminal of the power source is connected to the anode, where oxidation occurs, and the negative terminal is connected to the cathode, where reduction takes place.

Importance of Correct Connection

Ensuring the proper connection is essential because reversing the connections would reverse the reactions at the electrodes, which could be dangerous or simply yield unwanted products. As electrons are negatively charged, they are naturally attracted to the positive terminal of the power source, which is why it's crucial for the anode to be connected to the positive terminal to draw the electrons through the electrolyte and complete the circuit.