Which of the following chemical formulas represents calcium carbonate?

• A. CaO
• B. CaCl_2
• C. CaSO_4
• D. CaCO_3

Answer: (D)

Verified step by step guidance

1. Understand that calcium carbonate is a compound composed of calcium (Ca), carbon (C), and oxygen (O).
2. Recognize that the chemical formula for carbonate ion is \(\mathrm{CO_3^{2-}}\), which combines with calcium ion \(\mathrm{Ca^{2+}}\) to form calcium carbonate.
3. Analyze each given formula: \(\mathrm{CaO}\) contains calcium and oxygen only, \(\mathrm{CaCl_2}\) contains calcium and chlorine, and \(\mathrm{CaSO_4}\) contains calcium, sulfur, and oxygen.
4. Identify that none of the given options explicitly show the carbonate ion \(\mathrm{CO_3^{2-}}\), but the correct formula for calcium carbonate is \(\mathrm{CaCO_3}\), which includes calcium, carbon, and oxygen in the correct ratio.
5. Conclude that the formula \(\mathrm{CaCO_3}\) represents calcium carbonate, as it contains the calcium ion combined with the carbonate ion.