Which of the following are the most abundant solutes in seawater?

• A. K^+ and SO_4^{2-} ions
• B. Ca^{2+} and HCO_3^- ions
• C. Na^+ and Cl^- ions
• D. Mg^{2+} and NO_3^- ions

Answer: (C)

Verified step by step guidance

1. Understand that seawater is a complex solution containing many dissolved ions, but some ions are present in much higher concentrations than others.
2. Recall that the most abundant ions in seawater are typically the major contributors to its salinity, which are well-known from ocean chemistry studies.
3. Identify the common major cations and anions in seawater: sodium (Na^+) and chloride (Cl^-) ions are known to be the most abundant.
4. Compare the given options with this knowledge: K^+ and SO_4^{2-}, Ca^{2+} and HCO_3^-, Mg^{2+} and NO_3^- are present but in lower concentrations compared to Na^+ and Cl^-.
5. Conclude that the most abundant solutes in seawater are Na^+ and Cl^- ions, which together make up the majority of dissolved salts.