Which of the following substances is classified as a depolarizer?

Nitrates are classified as depolarizers due to their ability to enhance the discharge of electric charge within a system, particularly in the context of electrochemical processes. Nitrates, such as sodium nitrate, can facilitate the movement of ions, which is essential in various applications, including water treatment and disinfection processes.

In these contexts, nitrates can help to maintain the conductivity of water, allowing for more efficient electric current flow. This property makes nitrates particularly valuable in the realm of electrochemical reactions, where achieving consistent and effective current flow is critical for processes such as electrolysis and water purification.

The other options, which include cyanides, sulfates, and phosphates, do not exhibit the same depolarizing characteristics as nitrates and are not typically associated with enhancing the electric charge discharge in the same manner. Understanding the role of nitrates as depolarizers helps operators in managing water treatment systems effectively, ensuring optimal conditions for chemical reactions and overall water quality management.