What is the formula for chromate?

The formula for chromate is CrO4^2-. This polyatomic ion contains one chromium atom and four oxygen atoms, and it carries a -2 charge. The presence of chromium in the formula is essential since chromate is a compound of chromium in a specific oxidation state. Chromate is typically encountered in the context of its salts and solutions, and its chemistry is significant in various applications, including environmental chemistry and industrial processes.

The other choices represent different compounds or ions that do not correspond to chromate. For instance, C2H3O2- is the formula for the acetate ion, which does not contain chromium. CO3^2- is the carbonate ion, a totally different entity made up of carbon and oxygen, while HCO3^- is the bicarbonate ion, which also lacks chromium. These polyatomic ions serve different functions in chemistry and should not be confused with chromate, which has its distinct properties and uses.