Carbon dioxide (CO₂) is readily soluble in water, according to the equation CO₂ + H₂O ↔ H₂CO₃. Carbonic acid (H₂CO₃) is a weak acid. If CO₂ is bubbled into a beaker containing pure, freshly distilled water, which of the following graphs correctly describes the results?

Question

Quizplus · Accepted Answer

When CO₂ is bubbled into pure water, it reacts with water to form carbonic acid (H₂CO₃), which is a weak acid. This acid undergoes a dissociation reaction to release hydrogen ions (H⁺) and bicarbonate ions (HCO₃⁻) according to the equation:
H₂CO₃ ⇌ H⁺ + HCO₃⁻
This leads to a decrease in pH of the solution, making it slightly acidic. The graph that correctly shows this decrease in pH is option B.

Carbon Dioxide (CO₂) Is Readily Soluble in Water, According to the Equation