What is the ratio of HCO₃⁻ to H₂CO₃ in blood with a pH of 7.4?

• A. 20:1
• B. 5:1
• C. 1:1
• D. 10:1

Answer: (A)

Verified step by step guidance

1. Understand that the problem involves the bicarbonate buffer system in blood, which consists of HCO₃⁻ (bicarbonate ion) and H₂CO₃ (carbonic acid). The Henderson-Hasselbalch equation is used to relate the pH to the ratio of these components.
2. Recall the Henderson-Hasselbalch equation: ${\mathrm{pH}}_{}={\mathrm{pK}}_{}+log\left(\frac{{\mathrm{HCO}}_3}{H_2}\right)$. This equation will help us find the ratio of HCO₃⁻ to H₂CO₃.
3. Identify the pKₐ value for carbonic acid (H₂CO₃), which is approximately 6.1. This value is crucial for applying the Henderson-Hasselbalch equation.
4. Substitute the given pH value (7.4) and the pKₐ value (6.1) into the Henderson-Hasselbalch equation: $7.4=6.1+log\left(\frac{{\mathrm{HCO}}_3}{H_2}\right)$. Solve for the log term to find the ratio.
5. Calculate the antilog of the result from the previous step to determine the ratio of HCO₃⁻ to H₂CO₃. This will give you the ratio that corresponds to the pH of 7.4.