Alternate statement about the cations usually present in water in significant concentration: Which ions are usually the primary hardness contributors in water?

Alternate statement about the cations usually present in water in significant concentration: Which ions are usually the primary hardness contributors in water?

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

Answer: (A)

Hardness in water is caused by dissolved multivalent cations, especially calcium (Ca2+) and magnesium (Mg2+). These ions come from rocks like limestone and dolomite; as water percolates through these minerals, Ca2+ and Mg2+ dissolve and build up in the supply. They’re the primary contributors to general hardness, and when paired with bicarbonate, they create temporary (carbonate) hardness that can be reduced by boiling, which precipitates carbonate minerals as CaCO3 and MgCO3. Other ions such as chloride, sulfide, manganese, or iron may be present, but they do not drive hardness to the same extent. So, calcium and magnesium are the ions usually present in significant concentration that cause hardness.

Hardness in water is caused by dissolved multivalent cations, especially calcium (Ca2+) and magnesium (Mg2+). These ions come from rocks like limestone and dolomite; as water percolates through these minerals, Ca2+ and Mg2+ dissolve and build up in the supply. They’re the primary contributors to general hardness, and when paired with bicarbonate, they create temporary (carbonate) hardness that can be reduced by boiling, which precipitates carbonate minerals as CaCO3 and MgCO3. Other ions such as chloride, sulfide, manganese, or iron may be present, but they do not drive hardness to the same extent. So, calcium and magnesium are the ions usually present in significant concentration that cause hardness.