Which of the following lists the major species present when Na2SO4 is dissolved in water?

• A. Na+, SO4^{2-}, and H2O
• B. Na2SO4 and SO4^{2-}
• C. Na+, SO4^{2-}, and Na2SO4
• D. Na2SO4, Na+, and H2O

Answer: (A)

Verified step by step guidance

1. Recognize that Na2SO4 is an ionic compound composed of sodium ions (Na+) and sulfate ions (SO4^{2-}).
2. Understand that when Na2SO4 dissolves in water, it dissociates completely into its constituent ions because it is a strong electrolyte.
3. Write the dissociation equation: \(\mathrm{Na_2SO_4 (s) \rightarrow 2\ Na^+ (aq) + SO_4^{2-} (aq)}\).
4. Identify the major species present in the solution after dissolution: the sodium ions (\(Na^+\)), sulfate ions (\(SO_4^{2-}\)), and water (\(H_2O\)) as the solvent.
5. Conclude that the solid Na2SO4 does not remain in solution as a major species, so the correct list includes \(Na^+\), \(SO_4^{2-}\), and \(H_2O\).