Why is it important to rub the aluminum electrode with sandpaper before use?

Rubbing the aluminum electrode with sandpaper before use is important primarily for the purpose of removing the oxide layer. Aluminum has a strong tendency to form a thin layer of aluminum oxide on its surface when exposed to air. This oxide layer is generally non-conductive, which can significantly impede the electrical performance of the electrode in electrochemical applications. By sanding the surface, the oxide layer is stripped away, exposing the pure aluminum underneath. This enhances the conductivity of the electrode, allowing for better electron transfer during electrochemical reactions.

Consequently, having a clean and conductive surface is critical for obtaining accurate and reliable results in experiments involving aluminum electrodes. This practice is standard to ensure that the electrochemical properties of the electrode are optimal for the intended application.