Which test is used to identify carbonate ions?

The correct choice for identifying carbonate ions involves reacting them with dilute acid, which leads to the formation of carbon dioxide gas. When a carbonate reacts with an acid, such as hydrochloric acid, it produces carbon dioxide, water, and a salt. The evolution of carbon dioxide can be observed as fizzing or bubbling, indicating that a carbonate is present. This is a classic test for carbonate ions and is widely used in chemistry to confirm their presence.

Other methods listed, such as mixing with barium chloride, do not specifically identify carbonate ions; instead, they are typically used to test for sulfate ions. Adding silver nitrate is primarily associated with testing for halide ions, and heating with sodium hydroxide is often related to testing for amines or aldehydes. Each of these alternatives has its own specific applications, but they do not relate to the identification of carbonate ions in the same way that the reaction with dilute acid does.