If there is acidity in surface water, what happens?

If there is acidity in surface water, what happens?

• A. carbon dioxide will form carbonic acid
• B. sulfate ions form sulfuric acid
• C. chloride ions form hydrochloric acid
• D. nitrates form nitrous acid

Answer: (A)

Dissolved carbon dioxide forming carbonic acid is what makes surface water acidic. When CO2 from the atmosphere dissolves in water, it reacts to form carbonic acid (H2CO3), which partly dissociates to release hydrogen ions (H+). This increase in H+ lowers the water’s pH, producing acidity. This carbonic acid–bicarbonate system is a natural way surface water becomes slightly acidic and helps buffer pH changes under many conditions. The other options would require different chemical routes (sulfuric, hydrochloric, or nitrous/nitric acid formation) that don’t typically occur simply from those ions present in ordinary surface water, so they aren’t the usual source of acidity.

Dissolved carbon dioxide forming carbonic acid is what makes surface water acidic. When CO2 from the atmosphere dissolves in water, it reacts to form carbonic acid (H2CO3), which partly dissociates to release hydrogen ions (H+). This increase in H+ lowers the water’s pH, producing acidity. This carbonic acid–bicarbonate system is a natural way surface water becomes slightly acidic and helps buffer pH changes under many conditions. The other options would require different chemical routes (sulfuric, hydrochloric, or nitrous/nitric acid formation) that don’t typically occur simply from those ions present in ordinary surface water, so they aren’t the usual source of acidity.