Which equation represents the calculation for exact alkalinity?

The correct calculation for exact alkalinity incorporates the contributions from bicarbonate ions, carbonate ions, hydroxide ions, and the depletion due to hydrogen ions in solution.

Exact alkalinity is defined as the capacity of water to neutralize acids, and it is determined by several species in an aqueous solution. The bicarbonate ion (([HCO3^-])), the carbonate ion (([CO3^{2-}])), hydroxide ion (([OH^-])), and hydrogen ion (([H^+])) concentrations all contribute to the overall alkalinity.

In the equation that represents exact alkalinity, bicarbonate contributes one unit of alkalinity per molecule, and each carbonate contributes two units due to its potential to react with two protons (H+). The hydroxide ion also contributes directly to alkalinity because it can neutralize an acid, raising the overall alkalinity. Conversely, hydrogen ions reduce the alkalinity because they represent acid in solution that can react with the alkalinity sources.

Thus, the equation ([HCO3^-] + 2[CO3^{2-}] + [OH^-] - [H^+]) accurately accounts for the contributions and influences of all relevant ions in determining the total alkal