Emergency Medical Technician (EMT) Intermediate Practice Exam

Why is carbonic acid considered an ideal buffer?

1. It is a strong acid and can donate hydrogen ions

2. It is a weak acid and can accept or donate hydrogen ions

3. It has no effect on pH levels

4. It is neutral and balances all acids

The correct answer is: It is a weak acid and can accept or donate hydrogen ions

Carbonic acid is considered an ideal buffer primarily because it is a weak acid that can both accept and donate hydrogen ions (H+). This property allows it to effectively maintain stable pH levels within a physiological range, which is essential for proper biological function. In the context of buffering, the ability of a substance to either release or absorb hydrogen ions in response to changes in pH is crucial. When an acid is added to a solution, carbonic acid can donate hydrogen ions to counteract the increased acidity. Conversely, if a base is introduced, carbonic acid can accept hydrogen ions, mitigating the increase in pH. This balancing act helps to stabilize the overall pH of the solution. For example, within the human body, carbonic acid plays a vital role in the bicarbonate buffering system, which helps to regulate blood pH. This system is integral to maintaining homeostasis and preventing acidosis or alkalosis. In summary, the flexibility of carbonic acid to both release and absorb hydrogen ions makes it a highly effective buffer, allowing for dynamic responses to pH changes in various biological contexts.