Which chemicals cause alkalinity in water?

The classification of alkalinity in water is primarily associated with the presence of certain ions that can neutralize acids. Bicarbonates, carbonates, and hydroxides are the key contributors to alkalinity.

In this case, calcium carbonate and calcium oxide are substances that directly contribute to the alkalinity of water. Calcium carbonate (CaCO₃) dissolves in water to produce calcium ions (Ca²⁺) and bicarbonate ions (HCO₃⁻), both of which are essential for buffering and maintaining the pH level in aquatic systems. Similarly, calcium oxide (CaO) reacts with water to form calcium hydroxide (Ca(OH)₂), which also increases the concentration of hydroxide ions (OH⁻) in solution, further enhancing alkalinity.

Sodium chloride and potassium nitrate do not contribute to alkalinity since they consist of neutral ions that do not affect the pH balance in the same way. Magnesium sulfate and ammonium phosphate also lack the necessary components to significantly influence water alkalinity, as they typically do not dissociate into alkaline substances in water.

Thus, the correct assertion that calcium carbonate and calcium oxide contribute to water alkalinity provides a clear understanding of how these chemicals help maintain the pH