Which of the following is the correct name for the polyatomic ion CH3CO2-?

• A. Formate
• B. Oxalate
• C. Acetate
• D. Nitrate

Answer: (C)

Verified step by step guidance

1. Identify the molecular formula of the polyatomic ion given: CH3CO2-. This ion consists of a methyl group (CH3) attached to a carboxylate group (CO2-).
2. Recall common polyatomic ions and their names. For example, formate is HCO2-, oxalate is C2O4^2-, nitrate is NO3-, and acetate is CH3CO2-.
3. Compare the given ion CH3CO2- to the known ions. Notice that CH3CO2- matches the structure of acetate, which is the conjugate base of acetic acid (CH3COOH).
4. Understand that formate (HCO2-) is the conjugate base of formic acid, oxalate (C2O4^2-) is a different ion with two carboxylate groups, and nitrate (NO3-) is unrelated to the given formula.
5. Conclude that the correct name for CH3CO2- is acetate, based on its structure and common nomenclature of polyatomic ions.