What gas is produced when carbonate ions react with dilute acid?

A high-scoring answer should explain recall that carbonate ions react with dilute acid to produce carbon dioxide. Use method first, observation second, conclusion last: name the relevant test or measurement, state the observation, and then connect the result to Carbonate ions.

This is correct because limewater is the evidence expected for carbon dioxide, and turns milky is the result that supports the conclusion. A complete answer should use the approved objective wording, include the relevant evidence, and avoid unsupported identification claims.