Which are usually the only cations present in water in significant concentration?

Which are usually the only cations present in water in significant concentration?

• A. Chloride and Bichloride
• B. Manganese and chloride
• C. Sulfide and Iron
• D. Calcium and Magnesium

Answer: (D)

In natural waters, the major dissolved cations are calcium and magnesium. They come from weathering of rocks like limestone and dolostone and remain dissolved as Ca2+ and Mg2+ across typical water chemistries. These two ions are the principal contributors to water hardness, so they’re usually the only cations present in significant concentrations. Other options mix a cation with an anion (chloride or sulfide) or include metals that only appear in small amounts in most waters (like manganese or iron, which can be low except in certain settings). Therefore, calcium and magnesium best fit the idea of the cations typically found in significant concentration in water.

In natural waters, the major dissolved cations are calcium and magnesium. They come from weathering of rocks like limestone and dolostone and remain dissolved as Ca2+ and Mg2+ across typical water chemistries. These two ions are the principal contributors to water hardness, so they’re usually the only cations present in significant concentrations.

Other options mix a cation with an anion (chloride or sulfide) or include metals that only appear in small amounts in most waters (like manganese or iron, which can be low except in certain settings). Therefore, calcium and magnesium best fit the idea of the cations typically found in significant concentration in water.