Final answer:
To calculate the pH of blood with a PCO2 of 35.0 mmHg and a bicarbonate concentration of 24 mM, the Henderson-Hasselbalch equation is used. After applying the equation with the given values and the pKa of carbonic acid at body temperature, the result is a pH of 7.40, which falls within the normal range for blood pH.
Step-by-step explanation:
The student is asking how to calculate the pH of blood when the partial pressure of carbon dioxide (PCO2) drops to 35.0 mmHg, with a normal physiological concentration of bicarbonate ion (HCO3−) being 24 mM. To answer this, we use the Henderson-Hasselbalch equation, which in this context is pH = pKa + log([base]/[acid]). Since the pKa of carbonic acid at body temperature is approximately 6.1 and the concentration ratio of bicarbonate (HCO3−), the base, to carbonic acid (H2CO3), the acid, is 24 mM/1.2 mM, the calculation will be:
pH = 6.1 + log(24/1.2)
pH = 6.1 + log(20)
pH = 6.1 + 1.30 (because log(20) is roughly 1.30)
pH = 7.40
The pH calculation indicates that even with a decrease in PCO2 to 35.0 mmHg, the blood pH remains within the normal physiological range (7.35 - 7.45).