Which of the following is classified as a chelating agent?

A chelating agent is a substance that can form multiple bonds to a single metal ion, effectively 'grabbing' the metal tightly and preventing it from reacting with other substances. EDTA (Ethylenediaminetetraacetic acid) is a well-known chelating agent because of its ability to bind to metal ions, such as calcium, magnesium, and lead, and form stable complexes. These complexes can then be more easily removed from solutions or organisms, which is particularly important in water treatment and in various industrial applications.

In contrast, the other options listed do not exhibit this property. Chlorine is primarily used as a disinfectant and does not chelate metals. Sodium bicarbonate acts as a buffer in aqueous solutions but does not have the ability to form stable complexes with metal ions. Calcium chloride is a salt that provides calcium ions but does not bind to them in a chelating manner.

Understanding the role of chelating agents like EDTA is crucial in wastewater treatment processes as they can help in the removal of toxic metals, making water safer for the environment and public health.