Final answer:
To find the ratio of aspirin anions (A-) to undissociated aspirin (HA) at pH 7.4, we use the Henderson-Hasselbalch equation. The calculation shows that the [A-]/[HA] ratio equals 10^4 or 10,000 to 1.
Step-by-step explanation:
To calculate the ratio of A- to HA in the blood with a pH of 7.4 for aspirin, which has a pKa of 3.4, we use the Henderson-Hasselbalch equation:
pH = pKa + log([A-]/[HA])
Let's rearrange it to solve for the ratio [A-]/[HA]:
log([A-]/[HA]) = pH - pKa
log([A-]/[HA]) = 7.4 - 3.4
log([A-]/[HA]) = 4
Now, we can remove the logarithm by calculating the antilog (10 to the power of the value):
[A-]/[HA] = 10^4
This means the ratio of aspirin anions (A-) to undissociated aspirin (HA) in the blood is 10,000 to 1.