Alkalinity can be determined by the sum of which ions?

Alkalinity can be determined by the sum of which ions?

• A. bicarbonate, carbonate and hydroxide ions
• B. nitrate, sulfate, phosphate
• C. ammonium, chloride, sulfate
• D. sodium, potassium, magnesium

Answer: (A)

Alkalinity is the water’s buffering capacity against added acid, and it comes from species that can neutralize protons. The ions that provide this buffering in most natural waters are bicarbonate, carbonate, and hydroxide. They react with incoming H+ during a titration, preventing a sharp drop in pH, and the total alkalinity is essentially the sum of these base-form ions (usually expressed as equivalents of CaCO3). Nitrate, sulfate, and phosphate don’t act as bases in the same way to neutralize acid in typical waters, and ammonium, chloride, sulfate are not the base species counted toward alkalinity. Similarly, the alkali metals like sodium, potassium, and magnesium are cations and don’t contribute to buffering against acid. So the ions that determine alkalinity are bicarbonate, carbonate, and hydroxide.

Alkalinity is the water’s buffering capacity against added acid, and it comes from species that can neutralize protons. The ions that provide this buffering in most natural waters are bicarbonate, carbonate, and hydroxide. They react with incoming H+ during a titration, preventing a sharp drop in pH, and the total alkalinity is essentially the sum of these base-form ions (usually expressed as equivalents of CaCO3). Nitrate, sulfate, and phosphate don’t act as bases in the same way to neutralize acid in typical waters, and ammonium, chloride, sulfate are not the base species counted toward alkalinity. Similarly, the alkali metals like sodium, potassium, and magnesium are cations and don’t contribute to buffering against acid. So the ions that determine alkalinity are bicarbonate, carbonate, and hydroxide.