What is the relationship between CO2 and pH?

What is the relationship between CO2 and pH?

• A. Increased CO2 leads to higher pH.
• B. CO2 has no effect on pH.
• C. Increased CO2 leads to lower pH (more acidic), while decreased CO2 leads to higher pH (more alkaline).
• D. CO2 only affects pH when bicarbonate is high.

Answer: (C)

CO2 dissolves in water to form carbonic acid, which dissociates into hydrogen ions and bicarbonate. More CO2 means more hydrogen ions, so the solution becomes more acidic and pH decreases. Less CO2 means fewer hydrogen ions, raising pH. In the blood, this relationship is captured by the bicarbonate buffering system and the Henderson-Hasselbalch idea that pH depends on the ratio of bicarbonate to dissolved CO2; increasing CO2 shifts the balance toward acidity, while decreasing CO2 shifts it toward alkalinity. Thus, higher CO2 lowers pH, and lower CO2 raises pH.

CO2 dissolves in water to form carbonic acid, which dissociates into hydrogen ions and bicarbonate. More CO2 means more hydrogen ions, so the solution becomes more acidic and pH decreases. Less CO2 means fewer hydrogen ions, raising pH. In the blood, this relationship is captured by the bicarbonate buffering system and the Henderson-Hasselbalch idea that pH depends on the ratio of bicarbonate to dissolved CO2; increasing CO2 shifts the balance toward acidity, while decreasing CO2 shifts it toward alkalinity. Thus, higher CO2 lowers pH, and lower CO2 raises pH.