Which of the following species will be present in significant amounts in an aqueous solution of Na2CO3?

• A. HCO3-
• B. Na+
• C. OH-
• D. CO2(g)

Answer: (C)

Verified step by step guidance

1. Identify the species present initially when Na2CO3 dissolves in water. Na2CO3 dissociates completely into 2 Na+ ions and 1 CO3^{2-} ion, so initially you have Na+ and CO3^{2-} in solution.
2. Consider the behavior of the carbonate ion (CO3^{2-}) in water. It is a base and will react with water to form bicarbonate (HCO3^-) and hydroxide ions (OH^-), according to the equilibrium: \(\mathrm{CO_3^{2-} + H_2O \rightleftharpoons HCO_3^- + OH^-}\).
3. Recognize that because CO3^{2-} is a base, it will increase the pH of the solution, producing OH^- ions, so OH^- will be present in significant amounts.
4. Understand that the bicarbonate ion (HCO3^-) forms as an intermediate species in this equilibrium, so it will also be present in significant amounts.
5. Note that CO2(g) is not significantly present in the solution because the system is basic and CO2 would mostly be converted to bicarbonate and carbonate ions; also, CO2 is a gas and not a dissolved species here.