Final answer:
The dissolution of CO₂ in water forms bicarbonate and hydrogen ions, which does not alter alkalinity due to bicarbonate's buffering capacity. However, an increase in CO₂ levels can lead to increased acidity and affect the solubility of calcium carbonate, impacting coral reef structures.
Step-by-step explanation:
The dissolution of CO₂ in water doesn't change alkalinity because the dissolved CO₂ primarily forms bicarbonate (HCO₃⁻) and hydrogen ions (H+) through a series of equilibria involving dissolution, hydrolysis, and ionization. When CO₂ dissolves, it first forms carbonic acid (H₂CO₃), which then ionizes to produce bicarbonate and hydrogen ions. This bicarbonate can act as a buffer, absorbing excess H+ ions, which maintains a relatively stable pH and thus preserves the alkalinity of the solution.
Dissolution of CO₂ can affect the solubility of calcium carbonate (CaCO₃), particularly in the context of ocean acidification. With increasing CO₂ levels in the atmosphere, more CO₂ is dissolved in ocean water, which through hydrolysis and ionization increases the acidity of the water. This could lead to an increased dissolution of CaCO₃, harming the structure of coral reefs.
Alkaline earth carbonates like CaCO₃, insoluble in pure water, become more soluble in water containing dissolved CO₂ due to the formation of hydrogen carbonate salts, which suggests a coupling between the solubility and acid-base equilibria within the environment.