While converting carbonate back to bicarbonate, how does recarbonation affect the pH?

While converting carbonate back to bicarbonate, how does recarbonation affect the pH?

• A. Raises the pH to about 10
• B. Lowers the pH to about 8.8
• C. Lowers the pH to about 6.8
• D. Buffers the pH to keep it stable

Answer: (B)

When carbonate is converted back to bicarbonate, carbon dioxide dissolves in water to form carbonic acid, which then dissociates to release hydrogen ions. Those extra hydrogen ions push the solution toward a lower pH. At the same time, converting CO3^2- to HCO3- changes the carbonate balance and activates the bicarbonate-carbonic acid buffer system, which resists large pH swings. The net effect under typical recarbonation conditions is a moderate drop in pH to a value around 8.8, rather than a huge drop to neutral or acidic or a rise to a highly alkaline level.

When carbonate is converted back to bicarbonate, carbon dioxide dissolves in water to form carbonic acid, which then dissociates to release hydrogen ions. Those extra hydrogen ions push the solution toward a lower pH. At the same time, converting CO3^2- to HCO3- changes the carbonate balance and activates the bicarbonate-carbonic acid buffer system, which resists large pH swings. The net effect under typical recarbonation conditions is a moderate drop in pH to a value around 8.8, rather than a huge drop to neutral or acidic or a rise to a highly alkaline level.